Tis life, split your stash up across multiple addresses. It's been like this forever.
No it has not.
I don't want ot oderail the discussion here.
Lowering the amount of BTC held in a single address reduces the attractiveness to an attacker.
Having 1,000,000 BTC on a single private key is much more risky in the event of a quantum computer breakthrough than having 1,000,000 private keys, each with a single BTC.
Yes, you are absolutely correct. I was referring to the last part, where he seems to imply at least to me that this risk -- the same risk -- has existed forever. It has not, it is an entirely new issue.
If satoshi is still around and has control of his private keys, I think he will move his BTC from P2PK outputs to a segwit or multisig script. Then we would see a new level of speculation: was it satoshi that moved his coins, someone who stole them from him, or has someone been successful in creating a strong-enough quantum computer.
If he does not do this soon, there will never be a way to cryptographically prove that someone is satoshi. Once the keys are compromised, the quest for the identity of satoshi will be pretty much over -- at least for those that want real evidence. This is all assuming that he is not dead. The more likely scenario is that those addresses will get compromised over time.
Or maybe someone who is not Satoshi, did not steal them from Satoshi, does not own a quantum computer, and simply happened to mine them during the early days! Just saying.

This is possible too, but that would be a mistake on their part. There is no reason to keep coins in addresses that are less safe.