Kotaku reports they have "learned" that Call of Duty: Modern Warfare 3 is in the works and will be released on Nov. 8, 2011, attributing this to "multiple sources," who reveal details about the story and game modes in the military first-person shooter sequel. They seem pretty convinced this is all bona fide, saying: "we've gone to great lengths to nail down as much as possible the veracity of our sources. We believe that the imagery and chief details are accurate. That doesn't mean things can't change before release, but this appears to be a full run down of where Infinity Ward, Sledgehammer Games and Raven Software is [sic] on Modern Warfare 3 as they add the final polishing touches." They offer a gallery of art said to be from the game, as well as a separate article that makes no effort to avoid possible spoilers. Here's a bit from the first article, which makes an effort to avoid such spoilers:

The single-player campaign, which appears to wrap up most of the unanswered questions and character fates of the first two Modern Warfare titles, also introduces new characters who appear to be destined for future Modern Warfare games, especially two Delta Force operatives codenamed "Frost" and "Sandman".

Multiplayer in the game returns with a chunky list of playable maps as well as two types of Spec Ops modes: "Survival" and "Mission".