To be honest, I'm pretty damn happy with this update.
I honestly couldn't care less whether they do a physical redesign or not. A screen size increase would be MARGINAL without having to make the unit larger, which would be a huge strike against them.
Creating a good upgrade often means figuring out what the biggest weak points are to the old, and fixing them, while keeping around the tried and true that really work. Look, I'm not a HUGE fan of the iPhone 4 case design I much prefer the 3G beveled design, it doesn't dig into your hands. But, from what I hear, most people who have an iPhone 4 really like that design. So, if I were apple, I would keep it around for a while longer. The areas the iPhone 4 was looking weak in were: A) Battery Life, B) Speed, and as much as many of us here don't care C) Camera usability. All three of these things were addressed, IN SPADES.
I had an original 3G, and then 12 months in, it suddenly died, and I had to get a new 3GS. I was pissed about spending the money at first, and I was mad that it didn't look any different from the 3G. Then I started using it, and WOW, what a difference. And over 2 years later, it's still 95% compatable with everything on the market, still completely usable. While the original 3G started getting phased out 18 months ago. Had I kept a 3G around for 2 years, I would have been SCREWED, but the 3GS still is quite usable after 2 years. But, the difference between a 3G and a 3GS is NOTHING compared to the vast difference between the 4 and 4S.
The 4 upgraded the screen and form factor from the 3GS, but not a lot of processing power, not a lot of battery power, so really, the 3GS is mostly an iPhone 4 with lower resolution. Meaning, in the modern world, the 3GS is a perfectly capable device. Where the real changes are is during the off years where they spend their energy upgrading the processing power. Meaning, the iPhone 4 is going to have an 18th month usable life (like the iPhone 3G), where the iPhone 4S will have a 30 month usable life (like the iPhone 3GS).
Trust me, if they had changed the appearence of the device, you would be ooing and aahhhhing so much, you wouldn't notice that they only marginally upgraded the hardware, just like they did with the 4. So, in some ways, it's better that they didn't. We're not going to get EVERYTHING.
I just bought a new MacBook Pro this year, on an off year. No physical redesign at all, huge processing increase. There was whining all over the place, I'm HAPPIER THAN A CLAM with the thing.
With 18 month contracts, only a very small percentage of the iPhone 4 owners would be upgrading, whether this be a 5, 5G, iPhone X, or whatever. Bottom line, the iPhone 4S is an upgrade for us iPhone 3GS users, not for you 4 users. And for us, it's awsome.
My ONLY dissapointment, is that they didn't put back in the stereo analog audio linein that they removed from the iPhone 4. I'm going to have to keep my 3GS around to be able to do stereo audio field recording. But I'm only 0.5% of the population who cares, so I wasn't expecting that.
If they keep doing this two year cycle, I'll be very happy, and it makes a lot of sense, seeing most people will only upgrade every two years.
Oh, and Siri is going to be absolutely revolutionary. Lol, I actually heard someone say, "People are going to look rediculous speaking to their phone." Isn't that what we already do, anyway? Who's going to notice the difference? If it makes it faster to write an email or essay on a cell phone than a desktop computer, I think that's a huge update...
Speaking of which, I wonder if they'll release Siri for Mac OS X. I'd love to have it on my Mac Book.