Because the most recent season of "Dexter" and the first season of "Homeland" both premiered on Showtime in September of 2011, the assumption was that both shows would return around the same time of year in 2012. And that assumption was correct, as Showtime has announced that both series will return on Sunday, September 30, with "Dexter" again at 9 and "Homeland" again at 10.
The announcement's a bit earlier than usual for this sort of thing, but it's also confirming the obvious, so it's not earth-shaking news, either. Everyone knows, for instance, that HBO will air "Boardwalk Empire" again in the fall, but it's not official yet.
I stopped watching "Dexter" a few episodes into last season — then was amused to see how the entire Internet seemed to figure out the "shocking" twist many, many, many episodes before the "Dexter" writers expected anyone to — but I loved "Homeland" season 1 (and was a big fan of the finale, which I know some of you weren't) and am very much looking forward to seeing what happens next.