There might be a lot of customers who might feel a bit displaced after some revelations were made about the potential of current Windows Mobile 6.x.x devices getting the upgrade to the Windows Phone 7 Series platform.
Kwan said “Because we have very specific requirements for Windows Phone 7 Series the current phones we have right now will not be upgradable”.
The one point where the HTC HD2 misses out on is that it has more than 3 dedicated buttons that's stipulated by Windows Phone 7 Series.
For its part, Microsoft says it will not abandon the current Windows Mobile 6.x platform once Windows Phone 7 arrives. The OS will be rebranded as Windows Phone Classic and retained for budget-minded smartphone buyers as well as business customers with 6.x-based apps.
source:
http://apcmag.com/microsoft-no-windows-phone-7-upgrade-for-windows-mobile-6x-devices.htm