As much as I'd love that it's not going to happen. Mike owns Rifftraxx, with MST he'd be an employee of Joel and Shout. He was pretty clear when the new MST3K was being kickstarted and there was some confusion about who was involved that, while he wished the venture nothing but the best, he (as well as Bill and Kevin) had no interest in participating.
With Rifftraxx they show up in a recording studio, lay down a track that they may or may not have even written, and then are probably home in a few hours. Easy money for them. No host segments or studio execs.
It's too bad because to be honest Mike era episodes were the only ones I saw as a kid and for all I knew at the time he was the only one to ever host it.Mike issued a statement saying that he wished the new show well, but that he was always kind of a hired gun on Mystery Science Theater 3000, and he never got any royalties from the DVD sales. I'm not entirely clear on how, but Jim Mallon pretty much screwed everyone over, so that he and Joel were the only ones who ever got any royalties from the sales of the DVDs. I believe this changed recently due to Shout Factory getting the rights from Mallon. Long story short, Mike Nelson is probably doing OK with Rifftrax and doesn't want to ditch that in favor of doing someone else's thing that he probably won't make as much money from.
While I've since learned to appreciate Joel I still heavily associate Mike with MST3K.