The other problem with that line of thinking is that Microsoft, in attempting to enter the phone/tablet market, is going up against two well-established competitors, both of whom have more experience with it and are just plain likely to be better at it than them. Android and iOS dominate the market; what the hell is Microsoft going to offer that would sway someone to abandon their existing tablet or smartphone for a glorified Windows Phone 7 (which, I'm pretty certain, has less market share than VTech "learning computer" tablets)?
They bankrolled their way into the console market so they can only be trying it with Win phones.
However Microsoft will still fail, everyone loves Google and Apple is like a religion....kids will not seek out the M$ brand of phone OS as it's pure geek brand and offers nothing significantly better.
Funny because that's the struggle an x86 Amiga OS would face in mass market.