I don't know. It does seem a little arrogant to me. He doesn't miss an opportunity to remind everyone how much work he did for DT. It's true I know but it never comes off well when you pat yourself on the back. But to ask the other 4 guys to put DT on hold while he scratches an itch, is selfish in my opinion. Yeah, the other guys can play on other projects while MP takes care of himself, but why should they have to? He asked, and they said "No". I think they should be commended for splitting this cleanly. I'm a fan of MP's and will miss him in the band. Yeah, he seems a bit "confident" but you have to admire his talent and ambition. He is a huge factor in the development and longevity of Dream Theater.
That said, do I think MP has played his last beat with DT? No. I'm sure he'll be back for a tour/album or whatever. He knows die-hard DT fans will "buy the shit" out of that CD. That's just good business.
And for the record, I dig Labrie's voice and love JR on keys. To me, they are the "real" keyboardist and vocalist of this band.
Peace.
Dave