If I had to venture a guess that I was required to bet the farm on, I would say that both the Nets and the Suns hold tight on everything throughout the off-season and then see how both Durant and Ayton perform throughout the first half of next season.
If Durant sticks to his guns and is a malcontent, and Ayton comes in with his new big contract next year and proceeds to play unmotivated, then I bet both teams begin another negotiation around mid-year. The Suns will look for a suitor to take Ayton, and then put together another package with whatever they get for him plus other goodies to try and get Durant. The Nets will likely be very much more motivated to trade KD for whatever they can get at that point, and the Suns will have more flexibility with an Ayton/three team trade to sweeten any potential package.