I actually like the trinity. I enjoy all three roles, and enjoy switching between them pretty regularly. The only way to get rid of it is to make every spec decent at all three at the same time, and that just makes everything bland.
A support role would be interesting. I think it could be done successfully in WoW if done right, but I doubt Blizzard would want to make a change that big in a game this old. Of course, that's what I would have said about LFD, LFR, CRZ, pet battles, etc as well, so you never know.