Also, no, S.U.N. isn't free-to-play (F2P), it uses a buy-to-play (B2P) and pay-to-play (P2P) model at the same time in regions outside Asia, and inside Asia it's F2P and B2P. In addition, MU is only free-to-play on some servers and pay-to-play gives you unique servers and a bunch of benefits, and heard they will probably be enforcing some payment plan across all servers in the future.
I highly doubt Huxley will be F2P, unless it runs with similar models of their past games. For instance, bringing about a very-observable gap (more-so then Planetside) between the free and paying players in terms of equipment, access, and capability, which would likely make you want to pay-to-play or but-to-play anyway.
On the other hand, maintaining a server for a MMOG with intense FPS elements is more stressful on servers then an RPG, and cannot see them footing the server bills without something helping them cover the long-term costs, i.e. constant expansions, periodic subscriptions, advertisements, etc.
Also, Planetside is only going to continue it's F2P model till March 24, 2007, and it wasn't ever planned to permanent, as it was more of an experiment to see if it would attract more subscribers.