Although there isn't too much information about the new iPhone 5, speculations say that it is going to be full of new and awesome features, like the possibility of having a video chat on 3g or 4g, the feature not being restricted anymore to Wi-Fi. Another interesting feature would be the face recognition which lets you use your face as a security passcode. The fact that the iPhone 5 is going to have dual core processors, and higher and more powerful graphics cards will push the camera to its limits, making higher resolutions available video recording, and giving you the possibility of making pictures more still and at a higher quality.
The dual core processor will also improve the speed of the touch screen, and make multi tasking a breeze. When it comes to a carrier for the iPhone, it is hard to say, because there are few which have plans for building a 4G network. T-Mobile would be a solution, since they already have GSM, or Sprint, which already has a 4G network. Other big carriers like AT&T or Verizon Wireless are at the beginning stages. Some say that Verizon is going to get the iPhone somewhere in 2010, but even though that rumor seems to be denied, it looks like Verizon will get the iPhone for sure in 2011 when the new iPhone 5 comes out. It is a certitude that the 3G version of the iPhone is going to be taken by Verizon, but the real question is if they can handle a 4G version.
It isn't sure whether Verizon is able to build a 4G network for the iPhone or not, as there is a lot of work to do and little time. With or without 4G, it is believed that a large number of people is going to switch their carriers from AT&T to Verizon, just being sick of all the issues AT&T hasn't taken care of yet like lagging on app restrictions. AT&T's restrictions have already caused massive numbers of iPhone users to jailbrake their phones, since JailBreaking comes with Cydia, which is like the AppStore, but for JailBroken iPhones only.
The HTC EVO and Palm Pre phones on Sprint network, which already has a 4G network, seem to be the contenders for the iPhone and BlackBerry phones, but there are little chances for them to take over considering the release of the iPhone 4 and the iPhone 5 coming out next year.