I have a feeling that his lens could turn out to be a 15-70mm f/4. APS-C users have been longing for a crop equivalent of the 24-105mm f/4L for ages and a 15-70mm would be equivalent to 24-112mm on a crop body. Of course, many people say that f/4 is not fast enough on a crop but there are lots people using the 24-105mm on crop right now and are happy but wish it were wider. I would be tempted to say that this would be an EF-S lens but I feel that this lens would be more expensive than the 15-85 and therefore would not be a big seller compared to that lens. Therefore, I think that this would be an EF 15-70mm f/4L IS USM, which could replace the 17-40 f/4. This way crop users wanting a weather sealed pro built lens would have a great standard lens with a better range than the EF-S 17-55mm f/2.8 IS USM, and if those users upgraded to full frame or decided to use two bodies, one crop the other full frame, the lens would become a wide angle zoom. Granted there would be terrible distortion on full frame at 15mm but the lens could be used on full frame for anyone taking their first step upgrading from crop to full frame.
Of course, the exact focal lengths I have stated maybe wrong so it could be 15-60mm rather than 15-70mm but I do see it starting at 15mm and ending at either 60mm or 70mm.
So it think the lens will turn out to be either an EF 15-60mm f/4L IS USM or and EF 15-70 f/4L IS USM. I know many people would hope it was an EF-S lens but as I have said, it would be to close to the EF-S 15-85mm.