Yes or no?
It seems like the theory that the blue haired member of Akatsuki was the 4th's teammate was always one of the theories that people at least tolerated (it's one of my favorite theories that had no direct evidence backing it, the other being "Sasori is alive"):
http://www.stoptazmo.com/showthread.php?t=20914
So I guess it's won't be too surprising to most people if that is actually the case.

