Given what Canon has released in the last 3 years, it's becoming more apparent that they are depending more on brand loyalty than worrying about what the competition is doing.
I expected all along that the 5d2 replacement would be a very minor upgrade with slightly better AF, video, and sensor performance. It's the same thing they did when they released the 1d4, which many 1d3 owners including myself skipped over because it wasn't worth spending the money for a slight upgrade. If the 5d3 is a 22mpx sensor with only slight improvements elsewhere, there will be almost no point in upgrading for about 90% of 5d2 users unless they either need a 2nd body or just want to upgrade for the fun of it. Of course, Canon loyalists who have not yet experienced a full-frame body will likely flock to it.