The date appeared briefly on the publisher's European blog, and there is no reason for why the info was pulled. It could be that either the site jumped the gun, or the info was wrong.
Dead Rising 2: Off the Record is the "what if" scenario of Frank West, not Chuck Greene, was the protagonist of Dead Rising 2. West, of course, was the hero of the first Dead Rising. The game started as DLC, but has blossomed into a full retail title.