tada -
I wouldn't count on Windows (Mobile/Phone) 7 compatibility. Rumors have it that WinPhone 7 is going to require quite a few things the Touch Pro2 does not have:
1. Processor (needs a higher end processor)
2. Multi-touch (TP2 is resistive "single touch")
3. Compass
4. Micro USB (TP2 uses Mini USB)
I'd say one year from today, maybe, WinPhone 7 devices will be hitting the market. The question is, want to wait a year?
Maybe 3-6 months from now devices will come out that can be upgraded to WinPhone 7. Look for the capacitive screen (multi-touch), the compass, and the micro USB.
Here's the
link to the rumored requirements from WinPhone 7.