And seeing as it's rumours season (when is it not?) if you're hanging out to get the latest and greatest and buy it new, wait just a few more weeks until CES/PMA.
If Canon don't announce anything then, then there's not much chance of a new body being announced before april (but even if they do announce it at CES, the fsm knows when they'll actually have stock on the shelves...)
But if you want to go second-hand and get a good deal, go for it sooner rather than later, 2nd-hand prices of replaced bodies do weird things around announcement time...
An awful lot of electrons were terribly inconvenienced in the making of this post.
Gear Photos
So when is it time to upgrade bodies?
When everything sags and your pants don't fit. :-)