According to game site 1Up, Nomura states at the end of a 704-page DISSIDIA strategy guide: "There are no current plans for a sequel. To be honest, I wanted to do one up until a few months ago. I even called [Mitsunori] Takahashi, the planning director, and [Ryuji] Ikeda, the lead programmer, to talk about sequel concepts — I told them to think about what they were going to do and prepare themselves [to make a sequel]. However, circumstances inside the company wiped that idea out... to actually make [a sequel] happen would be very difficult given the situation."
(That situation is probably, what, the development of mega title Final Fantasy XIII?)
"If a lot of fans ask for a DISSIDIA II, circumstances might change. I'd like to think about the matter again if that happens," Nomura added. With the way DISSIDIA is selling and with Square Enix's proclivity for sequels, DISSIDIA II seems like no-brainer — and is.