If apple is going to keep the legacy view frustrum, the screen have to be 1920x1280 on a 4.6" screen. I dont see that as impossible, the tech is there, the question is volume production.
For the sake of world peace, lets hope Samsung live up to the rumors and produce a 1080p screen for the S3. IP5 (or will it be IP Next?) would still get the bragging rights for the extra pixels and most likely marginally higher density, but it wouldnt be "resolutionary". If the SGS3 "only" have a 720p screen, we'll have to listen to that resolutionary crap again.