Well, Portnoy seems to reckon his name's been on the cards for a hell of a while. I'm going to trust him until told otherwise.
And I mean, to be fair, schedules are a bastard - specially if you're Mike Portnoy. Very poss that he could be axed from it due to timing issues. Just getting Mikael and Steven together at the same time's a chore. But Portnoy's been attached to it for a fair while, so I'm gonna keep him in my "mental log" of this project.