when you are rebuilding, you aren't really looking at production drop off. As for Nash, he still puts people in the seats.
I wouldn't be surprised to see him moved in the off season however...
But you aren't trading players that outproduce their contracts in salary dumps either because they can get you talent back. So even if they wanted to trade Dudley, they'd never let him go in a salary dump or for an expiring and a late 1st rounder as they'd love to do with Childress. They'll want talent back; if they don't get it, they'll just retain him. He's 25, he can perfectly be part of their future core, with Dragic, Gortat, Lopez
Plus, between what Phoenix should do - go into full rebuilding mode around those young players - and what they actually do there's generally a gap.