Microsoft will continue to support Windows Mobile 6.5 devices once WP7 launches and recently revealed that it will release new WM 6.5 smartphones for years to come.
The bad news is that WM 6.5 handsets, such as the HTC HD2 pictured here, won't be upgradeable to WP7. Microsoft's Charlie Kindel wrote in his blog, "To enable the fantastic user experiences you've seen in the Windows Phone 7 Series demos so far, we've had to break from the past. To deliver what developers expect in the developer platform we've had to change how phone apps were written. One result of this is previous Windows mobile applications will not run on Windows Phone 7 Series."