Officially, HTC still has not specified a date when the HTC Desire will be getting the Froyo update. Unofficially though, the Desire already has a custom ROM based on Froyo. A person with the username udk over at XDA forums has posted a video of Froyo running on the Desire. Along with Froyo, this custom ROM also brings 720p video recording to the Desire.
Here is a 720p video recorded from the HTC Desire -
No release date of the ROM has been specified, but hopefully it should be up for download in just a few days. Currently, a beta version (v0.3) of the ROM is up for download. The main advantage of a popular Android phone is that that many new features are added to it thanks to Custom ROMs from Modder.
In all probability, this custom ROM will be released by udk before the official Froyo update from HTC arrives.