Personally, I wouldn't count out Win Mobile too soon. Microsoft thoroughly understands it's negelected the product for years. Nearly 2 years ago Steve Ballmer fired virtually the whole WM management and dev team for gross negligence and has hired the smartest people inside and out to develop WM7. No-one knows anything about this as MS has played it very close to the chest. The kimono will be raised slightly at MWC later this month.
Another thing: it's the UI that needs to be updated, and perhaps some new APIs added. But the underlying WM operating system (not the part the user sees or interacts with) is solid, powerful, and very capable. It's fully multithreaded and multitasking, whch is more than you can say for many (believe it or not, the iPhone/iPad can still only run one app at a time - imagine the howls of derision if Microsoft did that).
Steveb knows MSFT's back is to the wall and the stakes are high with WM7, so - based on past experience - I expect some very comprehensivce smart moves by the company to regain marketshare, or at least stop the slide and position for the next tech rev. It's about a lot more than just the technical stuff - relationships with carriers, IHVs, developers, channel, users all come into play. I wouldn't be surprised if lessons have been learned from Zune and xbox people, so I wouldn't count WM out just yet.