I sincerely hope the cap stands forever.

I sincerely wish Bitcoins were truly fungible but clearly they aren't (yet).  The growing toolset of taint analysis makes this obvious.  Mixing services help a ton but are at risk.  If Bitcoin is fungible then how do we know which are in Satoshi's stash?  No, fungibility is an illusion for now.
I see your point; I suggest a compromise; allow some to be stolen (for the good of the community) (eventually) and burn the rest.  We only touch non-hashed coinbase coins.
I stand down from my position; even if the non-hashed coinbase coins are all allowed to be stolen I will stick with Bitcoin.  I am prepared for a roller-coaster ride.

Gold has some intrinsic value, gold coins have historic value well beyond that, and also, much of it in museums is made into art; it would be wasteful and very costly to send them into the sun.  Bitcoins have no intrinsic value; nothing is wasted and it would cost very little to render them useless.  Museums are spread out with a variety of security measures in place; non-hashed coinbase coins are all sitting in one place.
Hmm, this position literally encourages folks to strive to steal them.  Do we actually need to have them stolen to gain the benefits of waking everyone up?  You, I, and some others are already awake before they are stolen.  Can't we gain the benefits any other way?  If not (and I do respect your opinion/thoughts) then I do see your point.  Suppose we compromise and allow some to be stolen (eventually) and render the rest useless.

My preference would be to move the non-hashed coins for safekeeping; does come with two big problems;

1) who can be trusted?
2) how do we know when the rightful owner steps forward to claim?

The alternative is to make them unusable.  This is *not* taking them to be used; that truly would be stealing them.  Making them unusable protects the community.  Look, someone is going to steal them eventually.  If the original owner won't act to secure their own coins then the community would be remiss to leave them to be stolen and wreck havoc.

Anyone that believes letting them be stolen and used is the right thing to do is either naïve or doesn't care about the good of the community.  No, give plenty of warning; watch carefully for developments; be prepared to act *before* the coins are stolen.

For what it is worth, I will withdraw from Bitcoin if this isn't adopted in time.  I imagine many others will too.

Someone will sell at the right price.  Also, Bitcoins can be divided into portions less than a whole.

I have taken steps to pass ownership on when I am no longer able to control them myself.  I am going to improve my plan by directly the new owners to move my/their coins to re-secure them (we don't want anyone thinking they became orphaned).
If one's bank has potentially weak locks on their doors then shouldn't the owner move their funds to a more secure place?  If the owner doesn't then shouldn't the community act to thwart theft?
Only non-hashed signatures put the coins at risk.  All modern transactions secure signatures with hashes.  Only old enough transactions lack the hashing security.  Quantum resistant algorithms are an active area of study already, e.g. hashing.  Not using hashing to secure things now is dumb.

*If* one were to generate new coinbase coins now without securing them with hashing then essentially they are putting them up for grabs.  I propose we enhance Bitcoin;

After some point X, all subsequent coinbase transaction must be secured with hashing or they will be rejected.

This should be very easy to gain consensus for.  Someone would have to work to generate non-hashed coinbase coins now anyway.  If they want to throw new coinbase coins up for grabs then they should find another way to donate them rather than encouraging theft.

Me.  I can totally be trusted; ask anyone that knows me.  Hmm, unless I am unduly coerced.  Hmm, what about a multi-sig?  Gosh, it would just be so much easier if Satoshi et al would secure their coins instead of burdening the community.

Ah, I see!;
vs.
The former is not hashed, the latter is.  The hashing makes it QC-resistant.  Leaving the unhashed coins laying around is just asking for trouble.  If the original owner(s) won't act to secure these then the community takes on the responsibility.  If the community doesn't act then I don't want to hear any complaints later.

Are my coins secured with hashes or not?  If they are not then I will act to move them.  How does one determine it?

I own 16V9UivwWtp6iGsaRnWycUjZJBcDDQRmV4 (amongst others).  Two transactions sent coins to it.  Both are secured with hashing.  So, I'm ok, right?  Or are only unspent coinbase coins at risk?  I don't happen to have any coinbase coins so I don't need to worry about my own, right?

Ok; so we can derive a Bitcoin address from the private key.  The same algorithm is used in both transactions, right?  We still don't see the relevant difference.

The owner had best get on with securing his stash before they are taken.  Does it take a quantum computer to take them?  Can a classical computer take them in a reasonable amount of time/effort?  Should I be making an effort to take them?  In the meantime, the market participants should take the risk into a account and discount the exchange rates.  Or are we saying they already have?  I doubt it.  If/when a Satoshi coin moves then the markets will react.  Until then the working assumption is they won't ever move.  Since the movement would likely wreck havoc then there is something to talk about.  If enough "voters" want to eliminate this risk then they can.  Don't sit on a pile and expect the rest of humanity to ignore it.  If nothing else the rest of humanity can abandon Bitcoin for something else without that particular risk.

Shouldn't we instead move the car(s) to a more secure location until the proper owner steps forward to claim?

Oh.  What does it mean to be "paid directory to a public key, not an address"?  Let's compare https://blockchain.info/tx/0e3e2357e806b6cdb1f70b54c3a3a17b6714ee1f0e68bebb44a74b1efd512098 to https://blockchain.info/tx/4d32d3caa4fc7121e48c59e895ff50aa4a80763aea107e7fc82749885aac5e99 and try to see the difference.

Instead of destroying Satoshi's stash, how about if we create an address and move the vulnerable coins there for safekeeping?

Perhaps the quality of the private keys are in question.  If a private key is generated with good randomness then it shouldn't be vulnerable.  If a private key is generated with poor randomness then it is vulnerable.  If the Satoshi (or anyone else's for the matter) private keys are at risk then having them age out seems like overkill.  Let the lucky bad actors take them.  The owners of such can move them before they are stolen to an address derived from a superior private key.

If the quality of the private key isn't in question then what the heck are we talking about?  If I sign and distribute a bunch of messages using my private key then each of those messages give the bad actors more data to attack.  If I never sign and distribute even a single message then I am just depending on the quality & security/privacy of my private key.  The block reward comes into existence without any signatures.  Only outputs require signatures.  Move coins to a fresh address (one that has never been used to sign) and it is safe.

Destroying anyone's coins to eliminate the risk of them becoming active is wrong pure and simple.

Is someone worried that Satoshi or anyone else is at risk of being coerced?  Destroying their coins hardly seems the appropriate response.

https://en.wikipedia.org/wiki/Lattice-based_cryptography & https://en.wikipedia.org/wiki/McEliece_cryptosystem

No.  The private key and corresponding public key (a.k.a. your Bitcoin address) do not have to change at all.  Rather, if/when we change the DSA from ECDSA (which is QC vulnerable) to another DSA which is QC resistant then your wallet software will have to be changed to use the new DSA; that's all; nothing else.

If we don't change the DSA to one that is QC resistant then bad actors (with enough moxie) will be able to sign messages moving bitcoins they have no right to move.

Oh.  Where is ECDSA https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm used in Bitcoin?  If that can be changed without me giving up my current private keys and Bitcoin addresses then this whole topic is noise.
Found it; https://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm.  So, yeah, this topic is useless; move on.

0) I care most about eternal life; as such I don't see where the topic of old Bitcoin private keys matters much.

1) Within this pre-eternal lifetime, I do care some about my Bitcoins; are they vulnerable?  Can one imagine a quantum computer (or anything else) that could crack my private keys?  If so then when (the sooner, the better) should we develop a system that can resist it?  It seems to me it will take an active step to migrate to it.  After some point the current private keys shouldn't be honored anymore.  Anyone that misses the cutoff effectively lose their Bitcoins.

My bad; per Rule 144 http://www.investopedia.com/terms/r/rule144.asp there is a 12 month holding period effectively making arbitrage way too slow.

That doesn't match what I was told.  I have sent an email to Grayscale asking for clarification and will post the response here when I get it.

Apparently that only applied to the original investment; new funds going in now are converted to GBTC without any holding period at all.