Thanks for your replies.
I want to give my opinion here.
I think a good way to circumvent this problem is to not to limit the amount of BTC to 21M. Instead it should have a deterministic inflation rate of let's say 1%. This would have 2 benefits:
First the concept of mining as it works today could go on for ever. Secondly, deflationary forces such as loss of BTC, could be compensated for.
I general inflation as it is today is not a good thing cuz it takes monex from the savers to the speculaters, but if the inflation rate is small and deterministic it would be a good compromise.
What do you think of that?
I think that's a great idea. Energy and computing power will continue to fall in price, so in theory BTC could always survive even with tiny rewards for mining, but BTC deleting/accidental loss will be the thing that would really hurt in the long run, IMO. I think having some plan for that where the total of BTC can rise eventually is a solid one, though like others have said, we may not need to worry about this for some time.