I don't know if it will be 12 or not - but it will be more than 4. With 4, the other conferences (weak as they are) will complain if the SEC gets more than 1-2 spots. I mean - if Clemson and FSU join, they'll have a stronger argument for 2 of the 4, but even then it will be tight.
On the other hand - with a 12 team playoff, the SEC could get 8-9 of the 12 spots and walk away with a larger piece of the pie. I can't see how they wouldn't know for that and love the idea. Honestly - regardless of what happens, does anyone see the SEC EVER having fewer than half of the 12 playoff spots? I don't.