A world without block rewards

[achow101]

Also, one has to assume that mining will get more power efficient.. In 100+ years, if we still use the same amount of power per hash we have failed as humanity..

This. And in 100 years 1 BTC will be like the GDP of a small country, so the fees the miners get will be enough even if they get small amounts of satoshis.

You think bitcoin will be the dominant currency after 100 years? You think in 100 years we won't think of anything better?

Are we driving the cars of 1915 today? Has there been any progress between now and then?

Bitcoin is the prototype, the Alpha version. The one with the bugs and missing features and blockchain bloat and 7 TPS capacity. Sure, it can be patched and improved, but eventually someone will figure out a totally different way to do things.

Bitcoin will change. It will implement new features and things that make it better than it is now. Look at your own example. Cars of 1915 are still similar to cars of today. They are all built on the same basic principles and have the same basic functions. That is what Bitcoin will be in the future. It will still be called Bitcoin just as cars are called cars. It will be different, with newer and better features to improve user experience, security, and scalability while staying with Bitcoin's principles and maintaining the historical blockchain.

[jonald_fyookball]

Fee structure will evolve to handle whatever volume is there.

If we go to a %, such as 0.1%, it will be adequate even with
a very modest increase in tx vol from today.

[Hopalong]

Also, one has to assume that mining will get more power efficient.. In 100+ years, if we still use the same amount of power per hash we have failed as humanity..

This. And in 100 years 1 BTC will be like the GDP of a small country, so the fees the miners get will be enough even if they get small amounts of satoshis.

You think bitcoin will be the dominant currency after 100 years? You think in 100 years we won't think of anything better?

Are we driving the cars of 1915 today? Has there been any progress between now and then?

Bitcoin is the prototype, the Alpha version. The one with the bugs and missing features and blockchain bloat and 7 TPS capacity. Sure, it can be patched and improved, but eventually someone will figure out a totally different way to do things.

And around 100 people own most of the bitcoins...

Anyone who can make a guess about the size of the blockchain itself when the last coin is made?

[Bit_Happy]

...
...I also believe some bigger companies would invest in FREE mining to sustain the network. {They would be so invested in the blockchain, that they

would have to provide this service, to continue doing business}

I am not really worried about such a situation.. there are too many people who are passionate about it, for it to fail. 

"FREE mining to sustain the network" will happen, if needed.
If/when Bitcoin actually goes mainstream, then it will take only a small amount of BTC fees to reward the happy miners, since BTC will be worth a fortune in fiat/Dollar terms.

[futureofbitcoin]

...
...I also believe some bigger companies would invest in FREE mining to sustain the network. {They would be so invested in the blockchain, that they

would have to provide this service, to continue doing business}

I am not really worried about such a situation.. there are too many people who are passionate about it, for it to fail. 

"FREE mining to sustain the network" will happen, if needed.
If/when Bitcoin actually goes mainstream, then it will take only a small amount of BTC fees to reward the happy miners, since BTC will be worth a fortune in fiat/Dollar terms.

Not true. If bitcoin goes to $10,000,000 each, you can bet there will be a lot more people interested in compromising it than if it was worth 4 billion in total.

So there will be a need for more miners when bitcoin is worth a huge amount than when bitcoin is worth a small amount.

[jbrnt]

What happens, specifically to the price of Bitcoin and transaction fees when the block reward drops to a negligible amount?
Current fiat reward for miners operating at close to break even: 25 btc* 300 usd =7500 usd
Transaction fees required for the same mining power to run the network: 7500 usd/4000 trx = 1.87 usd

When the block reward drops to a negligible amount, blocksize should be a lot higher then now. Miners are agreeing to 8M blocks. Bitcoin price will be higher than current prices. It will compensate of the drop in block reward. The cost of mining rigs will be a lot cheaper than now with higher hashrates. We also have the difficulty mechanism to balance everything.

In this future scenario, miners mine large blocks. They collect the a market rate fee. The market rate fee is around 1/10 of a dollar at the future exchange rate. If these fees per block can sustain a mining farm, farms will continue to exist in countries with cheap electricity. Future ASICs runs on low voltage low current, farms can be decentralised. If these fees cannot sustain a farm, less miners will operate. Hardware manufacturers will have to slash their prices, making mining cheaper for new entrants. When mining has become non-profitable, the drop in hashrate will be matched by a drop in difficulty, enabling older generations of miners becoming profitable.

If Bitcoin is still in demand, the mechanism will find it's way to reach equilibrium.

[peligro]

No, miners don't pay transaction fees. They GET PAID the transaction fees from the transactions in the block they hash/verify.

My point is, when transaction fees are the ONLY incentive to mine (and that will happen eventually as a certainty) the total sum of the transaction fees must match the cost of mining the block they were included in. If the block costs more to mine than the value of the  transaction fees in a block, miners (most) will shut down. At least so many will shut down that the network becomes insecure and Bitcoin will die. 

Currently, at the existing transaction per block limit, that would mean that a fee of $1.5-$2 would have to be paid for EVERY transaction to be added to the blockchain. Alternatively, the functional or "real"  value of BTC should be ten times higher to compete with an average alternative payment processor. That is of course if you look at BTC from a purely transactional and transfer point of view.

So, I'm looking for ideas as to what the ecosystem as a whole will see as a solution to this. Either Bitcoin finds mainstream adoption and the price increases to at least match the cost of mining or the blocksize will have to increase to accommodate more transactions with a lower fee. Perhaps a bit of both.

Either way, if either are to happen, Bitcoin will need to find mainstream adoption before the block reward becomes less than the cost of mining. I think I read that Satoshi said that Bitcoin would be everywhere or nowhere in 20 years and this might be what he meant. 20 years is 5 halvings of the reward. We're almost 2/5s of the way there.

Of course, I may be way off here, this is all hypothetical

Miners can't await that the fees make up for losses of reward halving. The fees simply would have to raise to a level that bitcoin would die from. So for now they have to deal with mining becoming less profitable. Which means switchign off old miners and only letting the good ones run.

At the end... these profits will rise again when the bitcoin adoption is rising, more transactions happen and so the miners will get more fees as a reward. But the total profit will proceed to drop for years now.