9to5Mac has information that indicates that Microsoft itself will introduce two new smartphones next year, most likely at the CES event at the beginning of the year. 9to5Mac says that these two devices are the result of the Danger acquisition. Danger is the company that makes the Sidekick. Sharp will make the hardware for Microsoft.
One of the devices will have a slide-out keyboard and is called "Turtle." The second is a candy bar device and is called "Pure."
Of course, there is no real info in the rumors as to what the platform will be. It could be Windows Mobile 6.5, but it also may be the Zune with phone bits added in. The Zune phone rumors have been around for some time. It could also be a mix, meaning WinMo 6.5 with the Zune interface for media and the home screen, but all of the application compatibility of a normal WinMo device.
Personally, I am not putting a lot of faith in these rumors. Microsoft is doing its level best to get WinMo 7 out the door before the iPhone renders the platform obsolete, and the Zune HD just launched sans a camera or any application store. For Microsoft to spend any resources on this third platform makes little sense, and actually shows a lack of clear direction. I could be wrong though. We'll see what rumors and evidence crops up in the coming months and then see what the January CES show has to offer.