My guess is that Coach Walton would have the biggest effect on whether McNair decides to try and retain Giles.
If Walton openly campaigns to McNair for Giles to return, which he should, condering the Kings played their best ball when Giles started, then their is a good chance the Kings bring him back.
With the salary cap likely to stay the same or decrease this year due to COVID, the Kings have a good chance to retain Giles with a solid $3-4 million offer.
The biggest carrot the Kings can dangle to Giles is that he knows he has a spot in the rotation and they would have his Bird Rights, which would make Giles eligible for a big extension next summer.