Speaking to Strategy Informer during a live interview, Game Content Director Bogdan Bridinel said that whilst they couldn't be specific, they didn't mind saying that one was coming "one or two weeks before launch".
"The demo will be online sometime in the middle of August, I'm afraid I do not know the exact date. All I know is that we've already built it."
This seems to only apply to the Xbox 360 and the PS3 at the moment however - there's been no news on a PC demo.
You can read the full transcript .