The Pew Internet & American Life Project just released the "Future of the Internet III" report which has some interesting predictions. Among the most applicable to businesses is the idea that by 2020, there will be 20 billion cell phones in the world - and they will be the primary method through which people access the internet.
Wow .... think about it. Think of interacting with your favorite websites only through a 2 inch square screen. Many applications do it now .... Facebook Mobile; AIM mobile, Yahoo Mail mobile, etc. And certainly many more are creating specialized applications for the iPhone. This proliferation will only spill over to Windows mobile or the OS for Blackberry.
Check out this great summary article, as well as the full report.