People who are still persistent and full of hope that there will be a redesigned iPhone 5 are under the sheer delusion of geekness. You have to look at things through a businessman's, a marketer's point of view. After all, that is what Apple is. Not a geek boy, a world-wide company. You don't make more money than the Federal Bank without wondrous marketing plans, business tactics. Let me try to explain(like many other tried) why there won't be a redesigned iPhone 5.
1) Main thing about this Tuesday's event is iOS 5 and iCloud, more software than hardware i mean.
2) Apple worked so much on iPhone 4's current design. They state that antenna on the outside is a great innovation and won't be changing that. Plus, they just released CDMA iPhone 4 four months ago and it sold like crazy. Hell it's still selling. From Apple's point of view, iPhone 4 design is a cow still with a lot of milk to milk.
3) You have to think futuristic on these things. Think for a moment what can be new on the iPhone that will come out after this Tuesdays'. First thing that comes to mind is LTE capability isn't it? So i'm positive that there will be a LTE iPhone in 2012, of course there will be at least an announcement of an iOS 6 in 2012 too. So LTE capability is a huge thing and needs a new design. If they redesign the iPhone now, they will need another design next year, not a sane thing to do.
I think there won't be an iPhone 5 re-design this Tuesday mainly because Apple thinks that the iPhone 4 design can go on for at least 8-10 months. Come June, announce new iPhone and things get back in schedule(regular June, iPhone month schedule)
And unfortunately i am saying these still owning a iPhone 3G from the October of 2008, now without the lock button and extra slowness. I too would want an iPhone redesign especially after waiting this 4-5 months for a new phone but my logic is stating otherwise.