I had a thought..
Given that block mining rewards halve every 4 years and eventually disappear, miners' incentives to continue mining will be transaction fees. The standard "priority" transaction fee (as far as the Android wallet is concerned) is 0.0001 BTC.
I know that as of now some transactions are mined for free, but to my understanding, transactions that are mined for free have to be at least 0.01 BTC.
My thought is that in the future, transaction fees are likely to rise to a higher rate (let's say 0.001 BTC) and will be required for every transaction. If you don't have at least 0.001 BTC, you basically won't be able to send any BTC to another address, which would seem to render the remaining 5 decimal places useless.
Is there something I'm missing?