Unless your phone has a way to plug into a larger environment, there is not much of a future for it.
Windows Phone and win8 are merging closer and closer with each release. Both are far from perfect, but they have a game plan and they are beginning to execute it.
iOS and OSX are at an odd spot right now, but they will begin to merge as soon as Apple gets some leadership.
Android and ChromeOS are now under the same umbrella and both will be undergoing some major unification changes over the next few years.
Ubuntu is not yet released, but the video concept demos that I have seen of it are phenomenal, and should be what every smart phone OS should be looking to do.
Meanwhile there is BB10 and Firefox OS. These are both perfectly fine OSs in their own right, but there is no future for them in a world where your phone becomes a key component of your larger technology experience.