To get back to the original question, Astro is correct: Adobe says spring 2012. Given all the official and semi-official preview videos out there, I'm guessing sooner rather than later.
I missed this, but apparently Adobe also announced last year that there were moving to a two-year upgrade schedule for major upgrades, with one-year between minor releases (CS 5.5 for example). They are also adopting a new upgrade policy that apparently will mean no upgrade pricing for editions going back more than one full release (for example, no upgrades from CS4 to CS6. Bummer.)
I realize that Adobe doesn't have any real competitors for their market niche, so they can afford to be more forthright about their schedules, but sure would be nice if camera manufacturers were a bit more transparent about their upgrade schedules.
I wonder if it would help or hurt sales if Canon were to just say: "While we cannot lock ourselves into a rigid schedule because it would run the risk of denying our customers ready access to the latest improvements in technology, we are generally aiming for a X-year release schedule on our X-D line of cameras."