my suspicion is that the technology war will stop at 10 speed cassettes for a while. it gives about all the range and uintermediate steps that you could really want between 11-23. there might be some argument that a 12-speed cassette would give a nice spread from 11-27, but i'm not sure the pros would be all that interested.

bear in mind, too, that 10 is a nice, understandable number. it sounds good. 10 speed is a better number for marketing than 12 or 14 or 8 or 9.