For me personally I think a thunderbolt port would be too fat for the iPhone. I'm looking at the port on my MBP and I think if that was there, the iPhone would have to be made thicker. But this is all my opinion as I don't have a iPhone 4/4S in my possession to see for sure.
Also, if I'm not mistaken I think thunderbolt ports only works because it's directly connected to the intel CPUs.