No one says to keep the full resolution of a APS-H sensor when an EF-S lens is used. I mean when you will use a EF-s lens on a... say... 20MP APS-H sensor you will have 12-13MP effective resolution ( the camera will crop the 1.3 sensor to 1.6).
1. EF-S lenses do NOT cover the image circle of APS-H (Crop 1.3x) - and even if you get a format-filling image at some focal lengths, vignetting will be really bad and IQ will be terrible towards the edges/corners.
2. Especially the rear element of the EF-S 10-22 may very well be hit by the larger mirror in an APS-H camera - as long as we assume it will be a DSLR and not a mirrorless APS-H camera body.
3. Unfortunately Canonhas was dead wrong to introduce the EF-S mount for its APS-C lenses (Crop 1.6x). Nikon has done it 100% right and implemented the only sensible solution: only ONE lens mount for any and all lenses - FX and DX. And NO rear elements sticking into the body so they may be hit by a larger FF camera mirror. And especially the D4 and D800 offer perfect cropping solutions by automacially masking off parts of the viewfinder if a crop lens (DX) is mounted. Although I like my Crop camera (7D) and my 3 good EF-S lenses (10-22, 17-55, 60 Macro) I can cleraly tell how inferior Canon's EF-S concept is.
4. Actually, Canon is not even taking advantage of the theoretical EF-S advantage. Only ONE EF-S lens (10-22) has a rear element sticking into the mirror box to be closer to the sensor. ALL other existing EF-S lenses could have implemented with an EF mount without any changes to their optical design. And even the EF-S 10-22 could have ben quite easily designed to also work with an EF mount ... Nikon had no problem designing their AF-S 10-24 DX to fit into their regular F-mount.
5. I have no doubt whatsoever, that there will be a 7D successor with APS-C sensor (crop 1.6x). It will be better than the current 7D. It will most likely only be announced some time after Nikon launches their new DX pro-body (D400 or whatever they may call it).