The T-Mobile HD2 rom has already leaked and it's 6.5.3. There's no way it ships with WP7.
However, I wouldn't be surprised to see a "developer update" for the HD2 that updates it to WP7. The "home" button can easily be used as the "Bing" button that's required. Microsoft needs to get hardware with WP7 in the hands of developers and what's a better way to do that than a firmware update for an existing device? "we aren't confirming which Windows Phones will be upgradable at this time. stay tuned for updates at MIX 2010
http://bit.ly/93e1Cf ". So to me that means at least some phones ARE getting an update. I don't know of any other phones that have a capacitive screen and a snapdragon cpu.