Well, don't rely on me as an authority on the future of computers

Look at my history - I picked Commodore 64 and Amiga, got really good at each OS. And then Commodore died. I picked Mac over windows95 at first. That ended horribly, too.
The reason I bet on Android over iOS is that
1) I don't want to learn Objective C and iOS. I already know Java and Android is a fun OS with beautiful free docs.
2) Apple no longer seems to have a stranglehold on hardware manufacturers as Android devices (Nexus 10) seem nearly as fancy. Google is no slouch in design.
3) Android's java and (really weird)linux seem more in tune with "work junk" programming. Not a big deal, but a bit of an influence.
Make your OS choice based on the software you use right now. Or just get em all - honestly, computers are dirt cheap these days. And keep in mind that I'm a developer - I'm weird.