While there have been no official casting announcements for the next generation of Ghostbusters yet, Cera has reportedly been campaigning to play Oscar. The actor informed People magazine that during the filming of Year One, he constantly haranged director Ramis about the "Ghostbusters" franchise and potentially playing a part in the third movie.
(I loved) Ghostbusters! As a kid, I wanted to be Bill Murray's character. Harold told me lots of stories and I memorized every word.
Obviously this doesn't mean Cera is a shoe-in for a part in GB3, but it is indeed interesting "rumor" news, and you gotta admit that he's perfect for Oscar.