I don't expect Apple to ever allow 3rd-party keyboards.
However, I do expect them to come up with their own gesture keyboard. Typing has always been a significant problem for touchscreen devices, and enough people know about and prefer these kinds of keyboards that Apple is just going to do it.
I don't know if there's any kind of patent protection on the idea, because there's loads of clones out there. If there is, Swype probably owns it (IIRC, they're the original creators of this kind of keyboard), and they're owned by Nuance. Apple have good relations with Nuance (they power Siri's voice recognition), so licensing shouldn't be any problem at all.
In fact, I'm sure Nuance would love to have Apple license the gesture keyboard. Not only would it bring in lots of royalties, but it'd make the feature even more mainstream and a must-have for competing Android devices.