From everything I have read, the 7D, 60D, 550D, 600D all uses the same processor. The last review I read between the 550D and 60D shows a tiny bit advantage of the 60D in High ISO noise. My guess is it is a software tweak they did to push and make sure 60D looks a little bit better than their cheaper brother. But now seeing these preliminary results of the 600D, seems they push the ISO performance even a little bit more.
Unless its an actual change on the chip, I think they can do a software update for the other models to get this upgrade. But whether they would do it or not is another story....
