It's like the 80s and the begining of windows all over again but for mobile devices. The question is what will be the OS that can use the most software. Right now there are: IPhone OS which is very closed. Windows mobile also very closed and not sexy. Android which is open and has lots of backing by lot's of different builders. Many other smaller options. Moblin look very open too but.. when it will show up, Android should already available from every cellular providers.
What is funny in that mobile war is the position of Apple. Pretty much like when the first Mac came by at the begining of the 80s. They have a great product. But they are too closed. So it's going to be everybody against them. They can't win. Dell, HTC, Lenovo, Motorola, Philips, Samsung, Sony Ericson (on the open side this time) , and many others already have android phones.
I predict that soon when you'll want to build a mobile application, it will have to run on Android first. That way it will be available to everybody. The rest will be second thought. Just like the market for computer right OS now with windows. But this time the winner will be the open platform because it's been early in the market and the manufacturer will simply find it easier then going for windows mobile.