If an image taken during Comic-Con is legitimate, it looks as though Resident Evil 6 will be revealed at the Tokyo Game Show on September 15.
According to the person who took the picture, which was posted on the HellDecent forums, he saw the image on the screen while attending a closed door press conference at San Diego Comic-Con
No pictures were allowed at the meeting, said the poster, but he took one anyway, apparently.
The image, as you will see through the link, shows a logo and the date "15.09.2011."
Tokyo Game Show runs from September 15 through September 18, so until then, keep this tucked away in rumorville.