Replacement coming or not?
Probably in about two years.
Doubtful. Although the 6D is a pro body, it is mostly marketed as a step-up for Rebel users who want to move to full frame. The Rebel line changes approximately annually. Based on that, I'd expect the 6D line to have a similar upgrade interval, or at worst, only a little slower. Otherwise, by the end of a three-year upgrade period, they would have people choosing to upgrade from the 6D back to a Rebel because of extra features in the Rebel line.
There are already some people considering upgrading from the 7D to the 70D because the 7D is so long in the tooth. IMO, if Canon is paying attention, they won't be eager to repeat that mistake with the 6D. (With that said, I half expect Canon to fold the 7D and 6D together into a high-MP full-frame body in 2014, which would explain why they haven't bothered to upgrade the 7D.)
As for the clearance sale, though, as others have indicated, that doesn't say much about the update schedule. In my experience, clearance sales quite frequently indicate that a seller was being too severely undercut by online resellers and wants to lower their price, but doesn't want to make people mad who bought it at the higher price. To solve that problem, they put it on "clearance sale" (a.k.a. a "we're overstocked" sale) for a few weeks at the lower price. By the time that sale goes off, everyone has forgotten the original (too high) price, so they are free to raise the price to something in between.