People on here keep asking what a redesign would bring. Well, I'll tell you what I would like to see in a redesign.
Bigger screen
Durable design (no more fragile glass on the front and back)
Better antenna design
Curved edges (much like the iPad 2. Curved edges, still lays flat. This makes it feel much better in the hand. Personally, I like the feel of the 3GS much better than the iPhone 4. Feeling sharp edges against a curved hand just feels weird and unnatural. Imagine if something else you were to touch a lot was in a box shape

)
Tear drop design (If it is subtle enough to not make holding it in landscape awkward, it would help be nice to have it thinner towards the bottom in portrait)
Elongated home button (not necessary, don't even know if multitouch gestures here would feel natural or awkward)
Those, I think, are reasons for a new design.
Yes, the iPhone 4 looks classy. But I prefer functionality over looks. And if you can have both, even better. I think with a redesign, there could be both. But there is not both with an iPhone 4.
I will be buying either way because I am coming from a 3GS and it is just too slow. The main thing I am looking for is features here, not design. However, with the new design would come added features, such as bigger screen. But going from an awful 3MP camera to an 8MP camera that fits in my pocket would be great, although I still plan on using my 60D for important stuff. And going from whatever crap CPU is in the 3GS to a dual core A5, most likely underclocked a bit to save battery, will be nice. Also, the possibility of 1GB would be great. But even 512MB would be an upgrade. As for Assistant, I am excited about it. Apple always has a wow factor, and if this is it, you better believe it will work incredibly. Even the speech recognition on my 3GS doesn't have any problems. Gets all that I say almost every time.
And I understand that all you current iPhone 4 owners seem to keep saying that you don't want a redesign, are hoping for just a 4S, or think it shouldn't be redesigned because you like the current design. Chances are some of you, not all, are just saying that because you don't want to feel that your phone is inferior to the newest one. Or you want people to easily be able to see that you have the "latest and greatest." Well, get over yourself.
I am still hoping for an iPhone 5, but the facts say otherwise. People at Apple have been busy this year around. ICloud is taking a lot of hard work by employees, as is iOS 5. And with them designing the iPad 2 and Apple TV since the iPhone 4 release, they have had a lot on their plates. This seems to make up for the longer than usual wait. And obviously their design team hasn't just been sitting around doing nothing.
However, I still think it would be stupid for them to say, "Here is the new iOS 5! Here is the new A5 chip! And here is the new iPhone 4S!" The 3GS lined everything up. They also didn't need a new design then because they didn't have as much competition as they do now.
If Assistant is the wow factor and needs upgraded internals, they could very easily make the iPhone 4S be the low end model at $99 BECAUSE they want Assistant to be in the hands of more people. Look at what they did with the 4th gen iPod touch. They even upgraded their low end option so that FaceTime could be in the hands of more people. They could easily do the same thing here. Then a cheap 8GB iPhone 4 could be free with a 2 year contract. We just don't know yet!
Apple loves uniformity and unison. Take the iPhone 4. 4th generation iPhone, A4 chip, iOS 4, thus named iPhone 4! They could and should do the same thing with the iPhone 5, whether or not it is a redesign. However, it should be a redesign to keep unison. Take their 3 best selling mobile devices: iPad, iPhone, and iPod touch. The iPhone is the only one that is missing the tapered design.
I'm praying for an iPhone 5 with a new design. However, just a simple spec bump will be nice from the 3GS. But using that awfully designed iPhone 4 won't be so nice.
Its a place holder in their logistics and inventory system. Friend of mine works for a large international carrier in managerial level and has no idea what's coming. They only know it's the new iPhone but that's the far as it goes. These are the same guys who are responsible for day to day operations so that explains why you have something like iPhone 5 in the inventory lists as a placeholder. You have to be a top executive have real knowledge of future iPhones and those guys have nothing to do with these lists.
If you have to be a top executive, how come the CEO of China's largest carrier uses the term iPhone 5?