Missing Member: Bassist Michael Anthony, 2007 to the present.
Background: After decades of swearing it would never happen, the Van Halen brothers finally relented in 2007 and let David Lee Roth back into the group. They had little choice. An album and tour with Extreme's Gary Cherone in the late Nineties was a commercial dud and a 2004 reunion tour with Sammy Hagar was a nightmare of backstage tension that ended with the two sides hating each other more than ever. The choices were bring back David Lee Roth or hit the casino circuit with a fourth singer. But by this point in time, Eddie Van Halen felt that Michael Anthony had grown too close to Sammy Hagar, even playing in his solo band. Anthony said that he simply didn't want to sit at home and do nothing, but to Eddie it was treason. Also, Eddie's teenage son Wolfgang was a prodigy on the bass and guitar and he wanted him in the group. Michael wasn't even told he was out of the band. He learned it when he saw reports on the Internet.
Impact on Reunion: It definitely put a damper on things. Michael Anthony's background vocals are a key part of the Van Halen formula, and they were needed more than ever once it became clear that Roth's voice wasn't exactly in pristine shape after he came back. Van Halen were still able to play arenas, but the whole thing felt a little hollow.
Odds of a True Reunion: It would involve Eddie firing his own son or Wolfgang walking away on his own free will. Stranger things have happened, but this one feels unlikely. At this point, we don't even know if the band exists in any form. They aren't very good at keeping the public updated about their plans.