So, why did Cameron switch from NZ to California?

[Aaron]

Well, Agoura Hills is the location of Lightstorm's enormous new (planned) studio, so that's no surprise. As for Manhattan Beach... not sure.

I doubt if he's had a falling out with Weta, and I expect that wherever he shoots, he'll still be using Weta Digital heavily for the CGI. However, it would not at all surprise me if Hollywood forces have been conspiring to convince JC to work closer to home. Hollywood's collective ego has surely gotten a good few bruises from all these American movie productions that have been taken overseas recently. He's probably got some smokin' deal with tax breaks and everything... in the name of patriotism, of course.