Well, I went with the unpopular choice of GSP.
Why? only one reason. The long layoff and the injury. I can see a serious problem with ring rust having not faught for over a year. When he finally comes back, I can in no way shape or form expect him to just come back after over a year away and a serious (in some cases career ending) injury and pick up where he left off.
If he wasn't the champ and was just a contender. This would be a perfect case for him to have a "Gimme" warm up fight, before he faught for the belt. But since he is the champ, he doesn't get that warm up fight. He has to come at full strength and on his first fight back, face whoever is at the tip top of their game and at the peak of their performance level and he has to beat them, right out of the gate, after a seriously long layoff. That is a brutal hurdle.
I am more than pulling for him to do just that. I want him to come back and defend on his first fight back. And if he does, he will surpass everyone else in my book as the best PFP ever. But first, he has to do it. And personally, I hope he does.