Can you imagine Neal Morse playing The Glass Prison?
On keyboard? Sure. He's not a metal artist, but let's be real, Neal has done some stuff that is not significantly less heavy than The Glass Prison. TGP isn't exactly death metal, either.
Do I think Neal will be playing it? No, probably not—he may come out and guest on Repentance, but probably not much more. But I could see it.
haha seriously? I have zero interest in hearing this without JR and JP, I can't imagine why anyone would!
'Cause Mike's the one who came up with the concept and wrote all the lyrics, and he's 1/5 of the DT that played on it? I get that some people really don't like Mike Portnoy anymore (or maybe never did), and that's fine, but there are also those of us who never took sides in the [obligatory analogy incoming] divorce and would like to see the guy play a series of songs that we really like and is clearly important to him.
I don't go to concerts really ever (it's rare that a band I like enough to see plays in a location and on a day that is convenient for me), and there's no way I can afford to take a cruise. But if this was something that was playing at a venue <1 hour away from me, yeah, I'd go.
Looking at the line-up of bands, he'll have plenty of prog rock and prog metal vocalists and instrumentalists to pull from, between the Neal Morse Band and Spock's Beard, The Fringe, Pain Of Salvation, and Haken. Between even just THEM, he could put together a rotating line-up to performance the suite's five songs.
Just looking at that list, I'd say Gildenlöw is pretty likely. I also would totally expect to see one or more of the Haken guys, since they're pretty similar to DT musically and there's little question of their being able to technically play it. Maybe Richard Henshall or Connor Green. And Ross Jennings could be a candidate for vocals, though you could also say Gildenlöw is a possibility for that, or even Ted Leonard.
If Sherinian will be there, might be interesting to see him on it—but I'm not sure he's fast enough to play all of Jordan's parts. I honestly wouldn't be too surprised to see Jordan himself show up. He's only DT member who we know is on speaking terms with Mike, and his parts might be the hardest to find someone to replicate just from the bands that I know are there. It would also lend a greater degree of credibility. In fact, just thinking about it, I'd say Jordan is the only DT member I'd say is likely to show. The second-most likely is probably James, who I don't think would do it but could conceivably have had a reconciliation with Mike. JP just doesn't seem like the guy who goes and plays his own music under the "Mike Portnoy" banner, and lolnojmx.
EDIT: I cannot express in words how strongly I agree with bosk's and Mosh's posts just now.