The EF-S 17-55mm is from 2006, so it's not that old as lenses go (it's a year younger than the 24-105L). The 17-55 is sharper than the 24-105/4L IS, and sharper than the new 24-70/4L IS, when compared on the same APS-C body. No, it's not quite as sharp as the 24-70/2.8L II, but the latter is double the cost.
I doubt Canon sees the point in L-series build quality, weather sealing, etc., on an EF-S lens, since the 7D is the only compatible body that has decent sealing. It's also unlikely they'll bring out an EF-S lens costing $2K like the 24-70 II, or even close to that.
Instead of releasing optically excellent lenses for APS-C, Canon brought out the 6D which is getting down to the price range of the 'flagship APS-C' so people can buy even more expensive lenses.
The 17-55 remains the best general purpose zoom for APS-C.