Tough to say. GSP and Anderson aren't going anywhere in 2013. I actually think Aldo will KO Edgar and dominate the division for a while yet. Henderson has no immediate threat, including Pettis. Mighty Mouse will defeat Dodson and continue to rule over his four man division for the time being. Rhonda will continue to arm-bar her way to victory in 2013. Jon Jones faces no immediate threat unless Cormier moves down.
My guess would be Barao to Mayday.
And Cain... Cain will fall. A hungry JDS is coming for that ass. December 2013.