I am not sure the Windows precedent applies here. At the height of the reign of Windows the landscape as far as the competition goes was extremely different. To point out one of the many contrasts - Apple did not have the kind of money it has today or the strong auxiliary channels: apps, music, ebooks etc to support its main product line.

I don't think anyone can say the world is going to be 90% Android or 90% iOS as far as handhelds are concerned. It is a market that is still opening up and there are at least three distinct pricing segments in it. Plenty of space for the top 2-3 to grow without killing anyone else.