Jabba the Hutt will be added to Star Wars: Imperial Assault soon, with his own figure and set of cards. As in the 1983 movie he appeared in, Jabba doesn’t really do anything on his own, he just orders underlings to fight his battles. He forms a mighty fortress this way. You can make other characters attack in his name and defend him; as many as four at once. Jabba also comes with 10 health of his own.
The catch with Mr. Hutt is that if anybody fires in his direction, he’s toast. People only fear him because of his wealth and power, not his physique or his ninja skills. You get more resources while he has them, but if the defenses surrounding him are whittled away, Jabba becomes the easiest target on the board. And I guarantee you all other potential targets will be ignored when that happens — no one will be able to resist this one.
If you want more details, Fantasy Flight Games has published a long overview on how Jabba works. No specific release date is mentioned, but the pack is promised to be “coming soon.”