Last answer first. Fluctuation controlled? Who would control it and for whose benefit? It might be controlled, but I say it shouldn't. Now will fluctuations slow? I think they will as the system grows. Just see an elephant move vs. a mouse! Also, at some point, if crypto becomes a dominant currency, the issue will be other currencies fluctuating vs. it and not the way around!
Could it replace the current mostly fiat based system. It certainly might. I may write a post about it.