According to EW, Darth Maul will be returning in the next season of The Clone Wars. (They also have video!)
Well, mostly. Filoni acknowledges that the order to resurrect the Sith Lord came from George Lucas himself, who became more interested in his Phantom Menace creation while developing Savage Opress for the last season of The Clone Wars. Awesome as Maul was in the movie, he barely got to do anything before the old chop-chop. When asked if Maul’s return is motivated by the feeling that he was underutilized in The Phantom Menace, Filoni says, “I think in part.”
Filoni's biggest challenge, though, will come from the legions of fans ready to shout “No way!” at the very idea of a Maul return. But addressing the (un)believability of his survival could make for some interesting drama. “First of all, how does he survive getting cut in half?” says Filoni. “Plus, he fell! And also, don’t forget Obi-Wan Kenobi is still around, so I’m sure Maul wouldn’t be very happy with him.”
Cool! Maul was one of my favorite parts of the prequel trilogy, and I would've loved to see more of him. No word on how he survives into the Clone Wars, but hey: cloning, etc., etc.