Nokia's problem will be that they will simply be outnumbered by Android in the upcoming years (their threat is Android, not Apple). Nokia's apparantly solution is QT compatibility across Symbian and Maemo. Thus applications written for one will ideally work on the other with little issue. Then push Symbian down so all dumbphones eventually becomes smartphones running Symbian while Maemo is for the high end devices. Whether that will work, who knows. My money is more on Android but they have their own issues to work out too. For example, running everything through a byte code interpreter means application compatibility, but it also means that you aren't taking full advantage of the hardware.

Apple's path will be interesting since they will eventually have to break compatibility support with the existing iPhone models. Whether they set up their development kit to say scale applications will be interesting to see.

It'll be interesting to see where everyone is in the future. I wonder if it'll turn out like my prediction with Android having the dominant marketshare for phones, with Apple's iPhone and Maemo in its own markets (similar to how Apple has its own selective marketshare in PCs).