Would they continue to work back channels to try and get to the P2? Absolutely, but every non-P2 school should be doing the same thing. And I really don't think FSU would be a cancer as long as the B12 didn't sign a 10+ year media deal like the ACC (which is a terrible move anyway).
Their fans would be bad, but nothing compared to Utah, and at least FSU brings in money to offset the downsides.