I think this one is just sort of a placeholder to get them by for another year before they come out with a new phone with major upgrades. The current one is really good, sure there's some things that could be better but there's no perfect phone and there never will be, for every nitpick you could make about the iPhone you could make something about every Android on the market as well.
I think more than anything this is just to appease the people that have to have a brand new apple device each year. There wasn't really much they needed to upgrade right now. The thing constantly mentioned is the camera, which it might not be what some others have but the 4 still takes really good pictures, if you can't get decent pictures out of it you probably can't take pictures regardless of how many mp your camera has. They're probably just letting 4g get a wider coverage area before they go all in on that but by next year I'd imagine they pump out a new phone that utilizes it.
Releasing a new phone now is more about just giving people the new device than trying to blow people away with something new. The "what'll be on the next phone" stuff started shortly after the 4 was released and I'd imagine that'll just continue. Even though this one probably won't have a ton of upgrades they'll still sell a bunch of them and then next year they can roll out a brand new phone that has major upgrades & 4G and people will forget this one ever happened.