- The enormous consumption of energy necessary for mining.
Seriously. Anyone have a serious lack of electricity? Just don't listen to the FUD from greens about it. People will always have enought energy.
- What will happen when it is no longer profitable to mine Bitcoin?
Miners will stop mining it. Thats how the free market works. But I'm sure that either the bitcoin will be somehow improved till that time or the technoligies will step forward and we will get some kind of super miner.
- Bitcoin will end up being a means to store value, or will it be used as currency for micro payments?
I'm parying that with lightning network microtransactions will become cheap. It doesn't solve the problem of volatility but it will still help a lot.