Hitting one of those times where one just have to learn something completely new, and been interested in mobile development for a while (no concrete plan, just something fun in my free time)

At the same time I'd like to learn something that might proof itself useful in the future, and been wondering if I should figure out IPhone or Android apps? (for some reason just don't feel like Windows Phones)
I'm pretty keen on IPhone (Objective C if I heard right), but that's probably just because I never used an Android phone. (Regret changing from IPhone to BlackBerry, that's for sure)

Since I've not been following that arena, I figured it won't hurt asking here which one seems that it will be the most used 2, 3 years down the line?