"To resolve Desire's memory issue and enable the upgrade to Gingerbread, we will cut select apps from the release.
Look for status updates starting next week. We apologize for any confusion."
Later on, in its Twitter feed, the company answered to a follower that it is in the process of deciding which apps will make the cut and which won't, and those unavailable in the official update will be at your disposal in Android Market, if you want to bring them back on, after all.
source: HTC (Facebook & Twitter)