I think it's pretty well set now. Tibet is the destination, Next May is the timeframe. I waffled a bit on targeting the Great Wall and Terra Cotta Warriors trip, but that felt pretty touristy and didn't really address the main desire - crossing tibet.
I've been speaking with Edelweiss tours, out of Austria, regarding logistics, timing, equipment and general fitness required to navigate at 12,000+ feet elevation.
This is going to be a process with a fair number of goals along the way. Riding experience, travel knowledge, learning the language (both languages: tibetan and mandarin chinese..) and general health and fitness.
Time to make some lists...