According to iMore, the next iPhone will be released this fall. Although there have been rumors of a larger (4 Inch) screen, sources seem to indicate that Apple will stick with the current size, 3.5 inches. This is not to say that they are not considering a larger one, and we all know that rumors about Apple's pre-released products can be all over the board.
You can read the full article here:
iMore iPhone 5
In summary, they claim the new iPhone will have: