The always reliable Green Day fansite Green Day Authority is reporting that the band has apparently wrapped up recording in the studio. The site discovered this fact in a somewhat unusual way:

Back in November we learned that the band was recording at the same studio where they recorded American Idiot, Ocean Way Recording in Hollywood, CA - same place where they recorded previous albums as well. Someone decided to go check it out, and found the guys parking spaces reserved, pretty much confirming the band was definitely there recording. A few days ago another visit to the studio showed the parking spaces were no longer reserved, leaving us to assume that recording is done; though, with no official word from the band, we can't really make any promises.

The follow up to American Idiot is expected this year.