My dad just showed me this today. This shocked me almost as much as Jimmy Sullivan's ("The Rev[erand Tholomew Plague]" -- drummer for Avenged Sevenfold) death. Here's the article straight from Dream Theater's site.

This is also very interesting because if Portnoy decides to go to another band, there's a very strong chance he'll stay with a7x (if they decide to continue with the band after their current tour). However, he could also decide to work with Liquid Tension Experiment or any of his other projects. But wow.