HTC recently said that they will be working on updating their phones to 2.2, it was just announced maybe 2 days ago so there are no firm dates or a list of phones yet, but it seems like that was launched this year will be updated possibly around Sep/October (which kinda sucks cuz 2.3/Gingerbread is supposed to be releasing around then)
I'm new to the HTC/Android thing, but from what I understand, if you really want 2.2, you'll be able to root your phone with a custom ROM for 2.2 but I think that it will overwrite HTC Sense. It'll probably be a couple of weeks before it's ready though. People are just getting 2.2 on their Nexus Ones, this morning so people will need time to work with it before it's ready to be ported to your phone.
I'm new to the HTC/Android thing, but from what I understand, if you really want 2.2, you'll be able to root your phone with a custom ROM for 2.2 but I think that it will overwrite HTC Sense. It'll probably be a couple of weeks before it's ready though. People are just getting 2.2 on their Nexus Ones, this morning so people will need time to work with it before it's ready to be ported to your phone.