Bama won't make it.  Not one impressive win.  Mercer?  They had to come back to beat Mississippi State a four loss team.  Strength of schedule.  Yes  Auburn beat them, but now Auburn is a 3 loss team.
If you put Bama in you'll leave out two conferences, The BiG Ten and the Pac12.  That certainly isn't going to happen.  Clemson, Oklahoma and Georgia for sure. I have no idea who is going to make the fourth spot.  As I said before IMHO Ohio States loss to Iowa should kill their chances.  This is a conundrum.