That was supposed to be Namie fans, not just Jamie fans.
I second this. I am so NOT interested in Carter. Sure he turned out ok at the end, but that doesn't mean I want to read a whole book centered on him. I think you're a great writer, but I just can't care that much about Carter. The idea makes me cringe actually. Lol. Your best bet would be to make an epilogue for the Jamie fans who don't care for Carter, and a... more a spin off than a sequel, for Carter lovers. Sequels in my opinion, are meant to continue the same storyline somewhat, adding in more elements, etc, which would mean Jamie and Nate still being pretty central, too. You could make Carter's story one that could stand by itself, instead. So don't include Carter in the epilogue. You could be like, "As for Carter... well, that's another story." Haha. Idk!.