I am sorry if from my RE: post it seemed that I took your post to be offensive. Not at all. I was just curious to know whether what I know about EF and EF-s (and focal length) is correct or not.
Coming to my original post, what I tried to mean is that even if canon comes out with a, say, EF-S 30mm, would not the perspective remain the same as that of EF 30mm on an APS-C? The EF-S will probably just "optimized" (smaller glass elements probably) for cropped sensor. Therefore, for us APS-C photogs, it won't make any difference (probably) whether canon brings out an EF 30mm or EF-S 30mm. With APS-C both will capture the exact same picutre (FOV equivalent to something close to 50mm). Is there any difference in the FOV of EF-S 17-55 f/2.8 set at 50mm on APS-C and EF 50mm (any of the three/four) on APS-C? I think not. But I do not have the 17-55 so cannot do the experiment right now. The request for EF-S 30mm is also similar I believe, EF 30mm will also serve the exact same purpose.