Android is quite likely the biggest winner over the next few years. What I'm personally watching for is what RIM does. While RIM has the corporate market, they've been trying to break out of that. I'd expect the major battles to be between Android, RIM and Windows 7 Phone.
Yes, I'm watching RIM and Android carefully as well. Currently, I get crappy EDGE service at home (in Gainesville, FL) and have to resort to UMA (WiFi-based cell service) on T-Mobile in order to make/receive calls. Since Android should support SIP natively (eventually), there ought to be a Google Voice/SIP combination that replicates my UMA/Blackberry experience. Unfortunately, it looks like things will go backward for a bit before moving forward as T-Mobile plans to deprecate UMA and does not offer it on Android. It also does not look like Google Voice/SIP on Android is ready for prime time at present.