I guess I'm looking at the capabilities of the 7D and seeing it make a compelling case for more/better/faster EF-S glass to compliment it.
It seems to me from looking very closely at 7D images, that the current pixel density the 7D has, 17.8 MP, which would scale up to about 46MP on FF, means that better optical performance is needed for the 7D. Some of the current Canon lenses are simply not up to the task of maximizing the incredible pixel density the 17.8 MP 1.6x FOV sensors; chromatic aberration and insufficient resolving power is clearly a problem on the lower-end EF-S lenses when they are paired with the 7D's new, high-tech sensor. Canon's current EF-S lenses, including the 17-55, are not "quite" there on the 7D.
This is not just a Canon issue or problem--it's universal. Nikon's D3x for example, is showing the limits of MANY of the Nikon lenses in the older segment of their entire lineup, and only the very-best Nikkor lenses like the 14-24,24-70,70-200,200 f/2 VR, 24mm PC-E, and other similar "newest generation" primes and zooms are able to allow the 24MP FF D3x sensor to show what the SENSOR is capable of; so, if 24MP on FF is taxing lenses, it's not too hard to see that 17.8 MP on 1.6x, which extends to 46MP on FF, is causing the same problem, only a bit worse! The photos show this.
The problem with EF-S though is that it simply will NOT mount on FF or 1.3x Canon bodies; the EF-S specification is totally incompatible with anything but the 1.6x bodies, soooooo....Canon probably cannot afford (not enough ROI) to make a high-priced EF-S lens unless it has very wide appeal, meaning "zoom lens" and one that covers popular lengths and fits the budgets of the 1.6x body crowd. If Canon does make a 1.6x-friendly focal length, it would make more sense to make it EF, and not EF-S. I think though that the new 17.8MP sensors will see many lenses slated for re-designs: already the 70-200 2.8 L-IS USM is in a redesign phase, as they announced last month: The 70-200's upper end needs higher resolution to leverage the increasingly pixel-dense sensors that are here, and which will come over the next 10 years. The newer 70-200 f/4 L-IS USM was beating the older, higher-spec'd lens, so the refresh was definitely due.
Canon's newest 24,45,and 90mm Tilt-Shift lenses are another example of needing better lenses, so Canon WILL do what it needs to keep up with higher and higher MP counts--at least in the big-money lens categories. Those lenses had a BIG price increase over the same models from prior generations, but Canon wants its users to have some of the finest big-system lenses in the world,and they are already fulfilling that goal. EF-S lenses appeal to budget-constrained customers and the masses,and it seems to me that 17-25-35 MP on 1.6x will call for L-quality lens designs and builds.