According to techradar this is still a question. I'm sure many will be disappointed if HTC will not release android 2.3 upgrade, especially for their Desire and Desire HD,I'll be disappointed to find out I bought their phone and they won't give me official OS upgrades for a less then one year old phone.
This is tight to the fact that rooting the Desire doesn't look so easy or safe, and although I found two good guides here and here I'm still not brave enough to drop my phone unusable and loos the HTC warranty.
unless someone here already did it and can suggest a know safe way to root the Desire and Desire HD.
We'll stay tuned on this for the following weeks.