I see a few problems with a Sean Waltman return to the WWE...first off, he's going to be pretty limited because of his neck. Secondly, with all the history he's had in the past with Triple H, you'd think that if he does return it would be to RAW. But Triple H already has a "good thing" going with Evolution right now, and I don't see X-Pac fitting into the mix.
And returning to RAW would be another HUGE blow to Smackdown. But if the WWE were to bring him back and have him work Smackdown, it could be a good thing. Most obviously, he is a cruiserweight, and could add to the contention over the title. He's also got the whole DX history thing going and maybe, just maybe, teaming him with Billy Gunn would be enough to get Gunn over with the fans again.
I don't know, if he shows up with something slightly different, I'd be interested in seeing him again go up against RVD and everything. But if all he's going to have is crotch chops and eight bronco busters every match, keep him as Chyna's wannabe rock star lackee.