Upload & Sell: Off
I went through this dilemma when I only had a 7D and a 17-40 which was giving me an effective 27.2-64 with the 1.6 crop factor. I needed wider. The 10-22 would have been my choice for UWA on a crop and have an effective 16-35.2. But this one is an EF-S lens that would not work on a full frame body if I were to switch to FF. I know, buy now what you need now, and sell when you switch. For the essentially the same money as the 10-22, I picked up a 5D Classic.
This has worked well especially now that my kid is studying Industrial Design and needed a decent camera to use besides a P&S. He is enjoying the 7D and has a choice of lenses. In your case though, picking up a FF body will necessitate a UWA lens purchase also...