I'm convinced Apple will bring out a large iPhone, to bridge the gap between the iPad and the iPhone.
I was lucky enough to get a new iPhone4, and it is awesome. No massive improvement on iPhone3G (but I didn't have one of those), but numerous little improvements....
Anyway, this dodge picture gives an outline of current iPhone, and an extra outline for a proposed larger phone. The screen area on this example would 1.8 x the current screen area. Phone would only need to 14mm wider, and 0-10mm taller.
In my opinion, the iPhone is a little hand held computer. Bloody smart little phone. Touch screen is awesome, perfectly sensitive. Email is easy, camera is pretty good quality now, internet browsing is excellent. WiFi connection is automatically picked up when you are in range, so you don't use Mobile Data. So many little features to mention..... They have done a good job on this device.... BUT - I would be happier with a slightly bigger phone and bigger screen !! Heading back to the old "brick phone" days !!