I just watched the finale on fox.com, (I was coaching my 10-year-old's little league game till 9:30 last night), and unless I missed something, I think there might have been a loophole left... tell me if I'm wrong:
Jack left his father to die (via airstrike) on the platform. His father HAD the circuit board on him, as the Chinese dude gave it to him when they detected the copter.
The Jack/Dad confrontation happened right near the boat Phillip was going to use to get away from the platform and meet up with the submarine.
My question: Couldn't Phillip have gotten on the boat (which has a homing beacon for the sub to find it (Chang told Philip that), gotten away from the platform, and still met up with the sub, and gotten away to China WITH the circuit board? Remember the White House detected the sub returning to China.
Something tells me Phillip is still in play, and could resurface next season or the season after.
If I missed something that makes any/all of the above impossible, please tell me.