Personally I think people are overly optimistic about this.
It will be different, yes, but I don't think that the other band members (Petrucci in particular, who was still the main writer) were against going in the direction they went, the direction so many didn't like. There's a good chance this could just be continuing in that direction, except without a key player, making it doubly worse for all of you. But then again I actually like pretty much all of the Dream Theater albums so I was fine with them continuing as the band they were.
As for me personally... I am looking forward to seeing the album they produce after this. Maybe it will make things interesting, give way to some good songs (you know there's going to be something related to / inspired by this in some way). But then again, I'd also be looking forward to the next album if Mike Portnoy was still there. All this really does is add an extra element of risk that the album could be worse for his absence, or that it could end up not being made, which I was already afraid of.
Really I just hope a new album gets made, and I'll never know if it was better or worse than it would have been without Portnoy. So yeah, I didn't vote since it'll be "They will change", but impossible to know whether for better or worse.