In the word of rock n' roll it seems that for a reunion it's not a matter of "if", but "when".
Black Sabbath reunited, Van Halen reunited, Kiss reunited, Iron Maiden reunited, Helloween reunited... there are so many examples of band that "would never reunite" and yet they did.
What bands do you think, however, will NOT reunite and why?
For this potentially short list, I propose Nightwish. Everyone in the band and in the fanbase is in love with their current singer, Floor Jansen, and the original one, Tarja Turunen, was unceremoniously fired with an open letter that in short said basically "Hi, we feel you're a spoiled bitch and your husband is an asshole, you're out. PS: all the internet knows about it", and I don't think she will ever forget that. So I can't imagine a scenario when Nightwish reunites with Tarja.
Other bands you think will never do the inevitable? (btw, until it actually happened, I would have included Helloween in the list.... so really, never say never I guess)