While carriers are sometimes the cause of these delays, why is it that Samsung’s WiFi-only tablets have not been upgraded yet? My guess is it is because of the no-value TouchWiz graphical layer Samsung lays over Android’s native interface. If vendors would stop fussing with their ugly and generally useless GUI overlays (with the exception of the screen capture utility Samsung adds with TouchWiz), I bet these upgrades would be available a lot faster.
So vendors, dump TouchWiz, TouchSense, Blur and all those other GUI overlays. They add little or nothing and keep desired new features and bug fixes out of your customers’ grasp.