Ultimately, yes he did. He absolutely knows it as well.
Mike gambled...and lost. He gambled that the band would do what he wanted, and that he was irreplaceable. Whoops!
What Mike should have done was decide on his own that he wanted to just play drums for the next record and tour cycle and force himself to disconnect from the many hats he took on, and asked his former bandmates to take them on. In essence, mentally get to a place where he could concentrate on playing some killer drums, and just being a drummer for awhile until he found himself in a good headspace again.
The guy lost his father and best friend, and then during the grief process for that, had Dream Theater looking to make a new record, and then dealt with more grief by witnessing the guys from A7X deal with it. That's a lot on the head of Mr. Portnoy. But he expected Dream Theater to just do what HE wanted, or at least partially do what he wanted...and they did. They took a break. They set a date to get back in the studio, and his bandmates wanted him to continue.
Instead of doing it, and coping with what he was going through by disconnecting from certain aspects for a bit and just doing the record, he made it all dramatic (insert well debated and gone over details here).
Then he blows it with A7X (again, insert details and debate here), and finds himself grasping back at DT, at which point, they have moved on (and frankly, rightfully should have, considering MP made DT second potatoes in my opinion, whereas the rest of the guys knew not to bite the hand that feeds).
But my personal view on that aside, absolutely Mike knows he made a mistake. But at this point, all he can do is move on, immerse himself in projects, try and get himself a revenue stream that can continue to support his family in a manner they are accustomed to being in, and go with the flow.
Mike will ultimately land on his feet. But he (and I think the majority of folks looking at the situation objectively) know that he made a big mistake. We'll see him on stage playing Metropolis for the 30th Anniversary gig, I'm sure of it. But I highly doubt he'll ever be back in the band. They've moved on, and frankly, so should Mike. He's one of the most talented drummers out there. Opportunity awaits. He just needs to seize the day...