Based on rumours this past year, how about this:
New 1d = pro (largely sport/speed) market. Larger form factor.
New 3d (or 5dIII)= high end/pro studio/landscape FF, crazy high ISO quality, larger form factor, video for pro use.
5dIII (or 3d or 9d) = routine upgrade to 5dII (with special attention to improved AF with more points, and inclusion of flash commander) but overall pretty much as-is. Relatively affordable, small-form FF.
7d = pretty much as-is. Top of the line crop, but still relatively affordable pro-useable, sports/all-rounder
XXd = more than entry level, but without the pro features - consumer all-rounder.
Rebels = entry level.
Maybe 3d and 5dIII specs reversed (if only to keep "name recognition" of the 5d for video), with 3d being the relatively affordable FF, and the 5dIII staying the pro FF/video camera. Or even a 9d being introduced as a relatively affordable FF (pure speculation based on Canon numbering traditions)