Same can be said about Windows 7.
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Not a whole lot of change.
You are absolutely correct that not much, really, has changed. It just looks much better and got some new functionality.
iOS needs this. Apple doesn't need to change the 'fundamentals' of iOS, but rather the look of it (look at Windows 95 and Windows 7 desktop above. The idea is the same, but Windows 7 has a fresh, new, modern look).
Make it fresh. Make it modern. Make it 2012. Make it iOS 6.
Edit: and sure, iOS doesn't look bad at all. Anyone new to the iPhone or iPod touch will like it because it's all new and stuff. But if you give someone Windows 95 without ever showing him newer versions of Windows, than Windows 95 does fine too.
Edit 2
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Some other examples to make iOS 6 have a fresh look:
Add landscape springboard/homescreen
This might seem insignificant, but it really is huge. If iOS 6 brings us a landscape homescreen-support along with some other new UI elements, iOS 6 will really feel modern (even though the change is actually small)
Multitasking (iPad)
The current multitasking bar does fine. But that's it. It doesn't do great. It only does fine. If you think about it, the multitasking bar currently used is perfect for iPhone... but it's really terrible for iPad. The multitasking bar on iPad takes really little screen-space, and all the space above is useless. Apple could make a much better multitasking-experience on the iPad (by making use of the bigger screen).
Widgets on iPad
I think widgets on the iPhone would be messy, but I think widgets on the iPad would be great because of the big screen. Perhaps, widgets could be placed in a bar on the right (just like in Windows Vista).
Springboard
Redesign the springboard. Add (and change) some small UI elements. This way the OS will look fresh and new, while the changes are only small.
All the changes above are really small changes to the OS, but I believe they are important. The only 'big thing' is widgets for iPad... and heck, now someone probably will say how bad it is, well, guess what... you don't have to use widgets and you can disable them!
I also believe that Apple should make more difference between iOS versions for iPad and iOS versions for iPhone. One good example is multitasking (as I said above): make use of the bigger screen on the iPad! Make the iPad feel like a tablet, a small personal computer.