He's just not sure for whom yet (from MMA Weekly):

[Cesar Gracie] said he is already making plans for Diaz’s next fight. The 25-year-old fighter has an existing clause in his contract allowing him to compete in Japan as long as it doesn't interfere with his EliteXC duties.

"We’re not doing anything wrong if he fights in Japan," Gracie said. "As far as him fighting in the U.S., then the 30 day thing (applies)."

Gracie said representatives from Dream and Sengoku had approached him about using Diaz. Dream’s parent company, Fight Entertainment Group, is planning a K-1 Dynamite! event for New Year’s Eve, while Sengoku 7 is scheduled for Jan. 4.

Gracie (who trains and manages both Nick and Nate Diaz, Jake Shields and others) also sent EXC notice regarding a breach of contract due to the company's inability to fulfill its financial obligations to Diaz, as Monte Cox did for Robbie Lawler. Presuming no major legal snags pop up in the aftermath of the EliteXC meltdown, this is great news, since Diaz probably won't be landing back in the UFC anytime soon and there are countless great (or at least fun/exciting) matches waiting for him in Japan. How about that "Mach" Sakurai fight now?

UPDATE:  In more Diaz Bros. news, GracieFighter posted yesterday to let fans know that they won't be seeing Nate back in the cage for at least a couple more months. A rumored December bout with Clay Guida "never got off the ground due to a reported foot injury Guida sustained in his last bout" and the camp is of the opinion that "every viable UFC contender" is otherwise occupied at the moment. A late January return is mentioned as a possibility, on the UFC 94 card which will likely feature a main event of Georges St. Pierre vs. B.J. Penn.