I think this is good news. Gentry will give Walton a strong #2 to help coach this team.
Considering Gentry is 65 years old, he doesn't pose the same threat as a young, up and coming coaching threat to Walton, as a long term replacement. But he does offer a saftey net, just in case.
Gentry's experience should really help the Kings navigate the season. Plus, coming from the same GSW system, they should be familiar with each other and help with the meshing of coaching.