According to HTC, the Desire is getting a Froyo-based update in August, but unfortunately other smartphones like the Wildfire, Incredible and EVO 4G will not be as lucky. The global PR and online community manager at HTC, Eric Lin, believes they will be done with Froyo testing before Christmas, so that's when those other devices should expect an update. He also explained that it takes a lot of time to port all of their applications over to Froyo, and make sure that it runs well on all of their devices.
That is not like a one week kind of project or small task to do (which is true and reasonable). He also said that they need to make sure that all the applications are taking advantage of the Froyo features. Apparently, the HTC official said that Gingerbread (Android 3.0, reportedly) will be coming in the first quarter of 2011. So unless HTC already has an idea for their launch device, it may be a few months into 2011 before we see an HTC manufactured device with Gingerbread. Contrary to popular rumors, of course.