The iPhone 5 could launch in June this year, although there has been a bit of talk of it not showing up till September of this year. Either way, the iPhone 5 (or 4GS) will eventually arrive and with it, a few tweaks here and there.

The infographic embedded below, shows a number of changes that might happen to the next generation iPhone and also gives a percentage of how likely the change will be made.
Some of the obvious changes include an updated camera, perhaps 8 megapixels on the back. We also hear that the Home Button might be dropped in favor of the multi-touch gestures used on iOS 4.3 (for developers). This is a little less likely due to 4/5 finger gestures being next to impossible on the small screen. We hear a slightly larger screen will be used, perhaps 4 inches. Again, Apple has always used the smaller 3.5 inch screen with the only main difference being the higher pixel density Retina Display on the iPhone 4.
A new design is also hinted at with some believing the device will take design hints from the new iPad 2 with a flat metallic back and rounded edges. It is more likely that Apple will stick to the iPhone 4 design, perhaps with something to squash the antenna rumors that caused a stir last year.
A physical keyboard is on the list although we agree that it has a probability of zero percent.
Many more rumors can be found on the infographic below (created by Nowhere Else).