I'm not sure how these rumors (if true) don't constitute a major upgrade:
LTE (just because it isn't available where you are doesn't mean the speed difference isn't substantial. And am I the only one who thinks Apple waited to implement this until it was efficient enough for them? Ala Qualcomm's new chips)
In-cell touchscreen (this is getting lost. not only will the device be lighter and thinner, but the lcd panel will be closer to the front glass allowing for lower brightness and less power to achieve the same display quality.
Bigger screen (leads not only to more screen real estate - which is apparently what the majority wants - but also true 16:9 widescreen, smaller bezel a different sized handset overall.
Metal back casing (just because the phone is a rectangle with rounded corners doesn't mean changing the size and makeup of the phone itself is any less of a design change. Especially if this metal ends up being liquidmetal (highly unlikely)
Upgraded camera (heard rumors of a 13 MP, but not sure of their validity. At any rate I'm sure you can expect a 720p front camera for facetime and hopefully at least a 10mp rear camera.
Upgraded CPU/GPU (it will be faster and smoother....not sure how much clearer to be than that.)
Battery life (with all the high-efficiency chips and parts going into this new phone I wouldn't be surprised if it boasts unprecedented battery life versus previous models)
iOS6 (you know there will be a feature locked only to the iPhone 5. I know there are plenty of people who don't see this as an upgrade either but 3D mapping and turn-by-turn, Siri improvements, Passbook are only a few.
I'm not sure what else you people are looking for save a triangular phone with a holographic display or something completely absurd. The OS updates aren't there to introduce BRAND NEW ways of doing things, but to improve on the existing methods. There literally is an app for everything so it would be difficult to come up with some brand new thing to do with your phone at this point. If you put out a polished product, why is there any need to radically change it every couple of years?
That being said, based on the above features, I think this year's iPhone release will be the biggest upgrade yet.