A lot of people here are assuming that Sanchez is Rex's boy, and he'll probably end up going with him just because.
I disagree. Rex had already tied himself to Sanchez for 4 seasons, and it got his boss fired. For self-preservation purposes, it only makes sense for Rex to put as much distance between him and Sanchez as possible. We know Sanchez is gone, whether it be this year or next, but we DON'T know that Rex is gone for sure, and I imagine he hasn't exactly resigned himself to getting fired.
It only makes sense for him to go with Garrard or Geno. Otherwise he'll be exiting stage left with Sanchez and they can be as close of friends as they'd like to be.
Unless of course Rex still really believes Sanchez will be a good QB, in which case he deserves to be fired anyways. I still support a future with Rex Ryan, but if there is one thing that would rightfully get him fired, its that.