This was posted on a Russian site (which I can't translate), however, they are claiming this info came from HTC workers on the inside. I don't see any reason not to believe it since it's 11 months out and seems reasonable...
http://www.youhtc.ru/2010/01/htc-hd3-specifikaciya/
I have to say, those are "dream phone" specs. I may be switching to Android soon, but those specs are enough to make me reconsider. If it has 4G, it could only be bound for Sprint in the US. But like the HD2, it may be headed to Europe first, and Sprint nearly a year later, so I won't be getting my hopes up.