HTC Desire HD is not here yet. But its ROM is here. You can download HTC Desire HD ROM for HTC HD2 now. It is using Darkstone Kernel and in beta 2 stage. Some of the things like camera, Ebook reader, ringtones, video playback and LED notifications are not working. But you can try out the latest and coolest HTC Sense. Check out below video ~ HTC Desire HD Demo on HTC HD2.
Installation guide ~ How to install Android 2.2 Froyo on HTC HD2?
Download HTC Desire HD ROM here (beta 2)