I think it will survive until people believes in the technology. Since bitcoins can last indefinitely in theory, bitcoins will be relevant if there are people that are willing to buy and sell it. The 21,000,000 bitcoin cap is just the number of bitcoins that will go out in circulation. The part of mined block, is just actually rewards. Miners can still continue mining blocks even without rewards. I guess that's a good thing for us, since our transactions will still be written in the blockchain. But I don't think I'll live to see that day since it's so far away.
Well Said,
Basically, it's a matter of credibility, Though this platform is totally dependent on the internet so that people have some confusing matter. without the internet connection, you can't use this system so that you have to be dependent on other factors. this is a negative side of this system.
So far I know about this system, Bitcoin is totally controlled by an automated system and Bitcoin holders, So with the change of technology, anything can be possible in the virtual world. that is why there is no way except keep ourselves waiting and watching.