just like when the iP4 was released, two new phones are likely to be released.... last time, it was an 'updated' 3GS + a new 4. This time, it's likely to be an updated 4 + a new 5. The difference, I think is that the iPhone 4 update will be more than just reducing the memory to 8 GB (which will happen). It will also include an antenna redesign and possibly a different face plate.
I suspect the home button is gone from the iPhone, and in its place, you have a touch strip where the home button used to be, to allow for swipe gestures.