It is a surplus.After Didi, the pickings are VERY slim. I'm sorry, that's not a surplus. That's the bare minimum that every team should strive for.
Cozart/Didi + utility guy backup < Cozart/Didi + what you can get for Cozart/Didi
The deal doesn't have to happen this offseason, but it could. It could also happen a year from now. Having two starting-quality young shortstops, and keeping one on the bench, is a waste of resources.