Thanks to WWE Network I've been able to catch up on some of the 2004-2012 stuff I missed due to disinterest and pretending like I was a grown-up and all of that. There are a number of wrestlers I've seen from that period who were clearly popular with the fans and/or with WWE management, but for whatever reasons didn't become main eventers or last as main eventers. So whatever happened to...
Umaga
Died of a drug overdose a couple of years ago, sadly.
Heidenreich
Mostly retired, does occasional indy dates and has a son in developmental.
Shelton Benjamin
Doing reasonably well for himself in New Japan and ROH on occasion.
Great Khali (I know he's still around, but how did he go from unstoppable champion to comedy act?)
Very quickly, basically.
Chris Masters
Don’t even get me started. He was in the news a couple of years ago for ripping a goddamn tree out of the ground to save his mother from a burning building, and I don’t think anyone even called him to cash in on the publicity surrounding it. He’s improved drastically since his WWE days and could probably be a star if given another go.
Carlito
He stopped giving a shit once Primo came in and showed him up at every turn, and ended up going back to Puerto Rico to continue his career there. I think he does occasional indy dates and stuff as well.