The usb port is not connected to running the 622's functions, it is only for uploading images. A software update may be able to change that, but I doubt Dish would waste the hard drive space to do that. The last receivers that had a keyboard were the 7100/7200 dishplayers and the keyboards did not really do that much more than the menu/remote could do (yes the typing was faster on the keyboard but traveling through the menu's is better and faster with the remote). The keyboard on those units were very useful when connected to the internet, something the remotes were certainly lacking in. If there was something the keyboard could be made to do a lot better, Dish would have already developed it and we would all have keyboards.
Of course, with the 922 being able to work with the internet, a keyboard on that receiver would certainly make working with that receiver a lot more user friendly.