A user at the Hell Descent forums attended a press conference about upcoming Capcom games, where they apparently mentioned that more details will be revealed on September 15 during the Tokyo Game Show, and one of the slides had a logo for Resident Evil 6.
Back at E3 2011, a Capcom rep told the press, ”We know that a lot of fans want more horror back for the next one, the development team knows that as well and we read a lot of comments, messageboards, and ask for feedback, and there was a lot of criticism about RE5′s focus on action. I think that you’ll like the direction the dev team is shifting for the next one.”
Resident Evil: Operation Raccoon City takes place during the events of Resident Evil 2, and is a tactical squad-based shooter, a gameplay departure from the series, so it’s not such a stretch to think it’s not Resident Evil 6. RE6 could take place after the events of 5 - but that would also mean Albert Wesker would be dead, disappointing a certain voice actor.