This is a case where I'll wait and see what the real ISO capability of a production camera actually is. I'd guess it will be around 1000 - 1100. The tests I've seen so far indicate that the real raw ISO is the same or a hair better then the 70D, but for jpeg output, the dual processors are able to apply better NR, closer to what a home computer can do. That's good news for jpeg users.
I hope all the professional testers are wrong, and its better than the images they took, but they have the most accurate tests.