I doubt a residency will happen anytime soon. Regarding a 2 year fellowship, I believe UCSF already has a 2 year fellowship? Not 100% sure.
I'm just finishing my 1 year fellowship. 2 years would have been too long of a journey for me personally. However, I have to admit that there is a TON to learn in pain medicine, from surgical skills to pain theory, and I can see some valid reasons for a longer training period.