While that's not totally impossible, Apple wouldn't take the extra couple of months just to release the same design with different internals. Regardless of what Steve Jobs said about "resting on their laurels" the 3Gwas done simply because they had no competition, and they could easily get away with releasing the same form factor with new internals. Now that the competition is stiff they cannot. There will be a newly revised iPhone this year, and you can count on that!
The 3GS was the best upgrade ever. Form factor means nothing, the 3GS buyers in 2009 made an incredibly solid choice, even with iOS 5 that iPhone is perfectly usable and faster than some 2011 high-end droids. I'm not sure we'll be able to say the same thing about the iPhone 4 next year.