decided to call it quits and leave the band.
It sounds like he wanted a break, the band didn't. Granted, Mike is the hardest working man in Metal has been doing tons of side projects, (Hail, Transatlantic and Avenged Sevenfold) and got tired, apparently. So he asked for a break, knowing that DT was planning on starting to write a new album in Jan. They said they didn't need a break...I can understand their side...they haven't been working their tails off then asking everyone else to work around their schedules...but still: What is Dream Theater without Portnoy? In my opinion, nothing.
A lot of people in the DT, Mike Portnoy communities are blaming Avenged Sevenfold (imo a horrible band that's beneath his talents) for taking up too much of his time...who knows.
All I know is that it sucks. I can't imagine a DT without this guy sitting behind the kit. He's one of the best drummers I've ever heard.