Bitcoin is getting harder and harder to mine. Small players (e.g. students/hobbyists) cannot afford to invest 70% of whatever revenue they generated, and will sensibly be forced out of the game. It's easy when you play against Villabajo, and it gets more expensive when facing Barcelona :)

I would assume that with the current technologies, the game will end being played only by the big players, when the currencies will be reaching their top tier (getting more and more difficult to generate).