Carter (Baizen) not to come back; Bart باس, گھنگھور to return (from the living dead?) 

(From Livejournal):

Rebecca: Spill it! Who's the dead father who's coming back? My money is on Christian Shephard of Lost!
Nope. It's actually Bart Bass of Gossip Girl. How crazytown is that?! A source tells me that Robert John Burke (the senior Basshole) will be returning to the show in December, just in time to make it a very special Gossip Girl Christmas. P.S. When I hinted that "two blondes will be atwitter" I was referring to Lily Rhodes van der Woodsen Bass Humphrey and Gossip Girl herself (Kristen Bell), who will certainly Twitter the news!—but of course Serena also would count. Whaddya think of that twist?

Margo in New York: Will Carter be back on Gossip Girl? I loved him with Serena! And is Georgina gone for good?
My friends at the CW tell me there are currently no plans to bring back Carter (boo!). And Michelle Trachtenberg is starring in that other show that's not Parks & Rec or Community and was just picked up by NBC (Mercy), so she's otherwise occupied at the moment. We took your question to her, and she answered: "Georgina has taken a little trip. She's gone off with who she thinks is a Russian prince. But as Georgina goes, you never see the end of her. She always comes back and torments."