The wait is finally over. You can now install Android 2.3 Gingerbread on Evo 4G, thanks to the hardwork of XDA-Developers forum member preludedrew. The Rom is named Evervolv is based on Android 2.3 source code (i.e AOSP Rom). According to users who have tested it, everything in the package works, i.e, you will get working Contacts, Market, Gmail, Facebook, Wifi, Sound, Calls, Browser, etc.
The developer has not posted any changelog yet but user feedback shows that most features are working seamlessly. If you cannot wait to get your hands on Gingerbread, then this Rom is for you. Keep in mind that the developer is continually updating the Evervolv Rom, so keep checking back at the official XDA Developers thread to download the latest Rom.