I think the iphone displays are manufactured by Samsung which might explain why no screen size upgrade took place.
I think LG makes the iPhone 4's IPS displays.
But in any case, the iPhone 4S announcement yesterday was a big bag full of fail. The only features that would incline any current iPhone 4 user to upgrade is the 1080p recording ability. The dual core A5 might be nice, but it probably doesn't improve the performance over the iPhone 4 significantly enough to justify the cost/contract extension for most iPhone 4 owners.
And Siri? What a joke. The day I start talking to my f***ing phone...
But the biggest fail for the 4S is keeping that tiny screen for yet another generation. Even if they kept the overall form factor/design the same but with a 4" screen, I think many people would consider upgrading or switching to it, but with that 3.5" screen it's just a joke (especially on Safari because you have the navigation button bar at the bottom taking up more space since there is only a home button on the iPhone).
I expect the Nexus Prime, with it's larger, HD screen with on screen 'buttons' and curved, sexy form factor (although I prefer a non-curved phone for media and storage in my pocket reasons) to blow away the surprisingly underwhelming 4S. Of course, the E4GT (and other GSII varieties) already does (blow the 4S away).