There's always the possibility, but not clear the marketplace will create room for them. Timing is everything, and they are late to the party.
To me, Microsoft has developed a reputation of a large company adapt at copying and more of a relic of the PC era. They failed with the Zune and MSN Direct for mobile devices. But XBOX has been a success both technically and I think from a marketing perspective as well.
I read how Elop was a driver behind Nokia going with Microsoft, and there appeared to be good reasons. But given his background with Microsoft, I always wondered if there was a bias that drove Nokia in that direction.
Anyway, I wouldn't be surprised either way, but I wouldn't bet much of my own money on Nokia's success.