If it was a mirrorless camera I would've expected new lenses to be announced - or maybe EF-S really is appropriate enough in this segment. I wouldn't expect them to show a new mount (seems wasteful) and I really wouldn't expect them to show a new mount without a lens, or to show the camera with a new lens but not "announce" it (how would that work anyway?)
Anyway, interesting stuff. Perhaps this means more buyers will be entering the realm of interchangeable lenses soon - I used to think that the TS-E on a low-end T1i was pretty unusual, but imagine tilt-shifts or Super Telephotos on a mirrorless body o_O