My guess would be that the next iPhone will look more or less the same. I would not be shocked if they made the screen slightly bigger and/or added that LED notifier everyone seems to want so bad.
Those aren't features I really care about, I'm just thinking that it's possible they might be added since Apple seemed to listen to customers on this current design- LED flash, front camera etc. I really don't want a bigger screen- I like the current size. I am never going to try to watch a movie on my iPhone from more than a foot away.