Taking a close look at the exterior antenna, one can see that there are now 4 spaces between the antennas instead of 3 so there appears to be a 4th antenna or antenna component. There are now reports that Apple has addressed the "death grip" antenna problems that degrade reception when the antenna is held a certain way. When the antenna is covered by a hand in the right position, this can happen. Because the antenna is around the border of the phone, it can happen in normal use unlike other phone where it is embedded near the top of the phone where a person would not naturally hold it. Reports are that Apple has duplicated antennas so that when one is covered degrading reception, the other one should be unobstructed and function properly.
Let me know what you have heard and if you have other information about the antenna design. In the mean time, I am looking forward to getting my wife one and I may wait for the iPhone 5 which is rumored to be available this summer.