Not sure why everyone's emotions are riding high on whether the 5th iPhone will look like the 4 or if it will have a new design. Upgrading the internals is more important than the exterior.
iPhone 4 design with upgraded internals like 8MP camera, A5, 1GB RAM, Assistant, etc = SUCKS!
New design with upgraded internals like 8MP camera, A5, 1GB RAM, Assistant, etc = OMG YAY
The exterior is something you'll appreciate for a few days and then its back to regular iPhone business. But I do sympathize with those that wonder what the hardware team was doing for an extra 4 months if the design was the same.
But in the end, the internals are more important. Think of comparing a 3G to a 3GS today. 3G iPhones are completely crippled, slow, with none of the nice tricks if iOS 4. 3GS can almost do everything an iPhone 4 can do and it will still get iOS 5 and iCloud support.
In the long run, what happens inside will be more important...
A larger screen is something that would hopefully come with a redesign that is something you will appreciate for more than "a few days", probably the duration of your phones existance. Its not multiple color options or changed shape of the home button people are screaming for its a larger screen.