From this week's chapter he figured out what the "heart was". "Oh, I see, it's this here in my hand". Going back to what Kaien had talked about, it seems as if Ulquiorra entrusted his "heart" to Orihime, just before death. So I believe he is dead, Ulquiorra finally understood that the heart and soul was the "bond" between two or more people when they make contact and such.
So I'm saying he is definitely dead and that he entrusted his heart to Orihime, the whole captor captive thing. Uh...he talked before about Ichigo going to their side but it seems that had this gone on Ulquiorra would have been the one to flip, he started gaining interest in "you guys" and then at the end it seems that KT was portraying (as I said before) that he entrusted his heart to Orihime. So..Iono that's my take on it.
It seems that as a hollow he was hungering for something, and he found out what that was with the "heart" and he fulfilled that demand at death, thus, he is no longer a hollow, so he died. If that makes any sense. Just looking at it from a literary sense that is.