Good news! As long as your son remains continuously enrolled in a Georgia public institution, he can maintain his in-state tuition classification status, even if you move away.
However, if he were MY son, I would make sure that his Georgia affiliation is well-documented (e.g., he should continue holding a Georgia driver’s license—if he has one now—and he should register to vote in Georgia). That way, if he does decide to interrupt his education … either intentionally (for instance, for a “Gap Year”) or due to circumstances beyond his control (such as serious illness or family crisis) … he will have established a “paper trail” that shows that he still has Georgia on his mind and not your new place of residency.