I'd like to see him fight Mayweather. It'd be an interesting match with a ton of hype, and good for the sport. Also losing to Mayweather still gives him a lot of options as opposed to say Cotto. A cotto loss isn't as forgiving as a Mayweather one. Though I'd like to see Mayweather fight Martinez... Best of the era/154 vs the top dog at 160. I'd like to see Cotto if he beats trout fight Canelo, it's a good closer match-up and seems to be an exciting one. I'd also like to see Martinez fight Mayweather. I realize I put that in reverse but I'm saying the best possible options for the fights if you're going from A to B.
Canelo -----> Mayweather
Mayweather ------> Martinez