Coming May 2011?
A replacement of the EF-S 17-55 f/2.8 IS could take the form of an EF-S 15-60 f/2.8 IS. It would have the same build quality of the current 15-85. May 2011 was mentioned for an announcement.
I've seen similar stuff about the 17-55 in the past. It's a lens that could use a refresh to keep the EF-S range from becoming stagnant. Canon is committed to APS-C.