A chef friend was once asked for the recipe for something he had put together for lunch. Of course there was no recipe - he had just made it up at the time. He said, There are no new recipes any more. There are just variations on a theme.
I think what he was really saying is that existing recipes are used to springboard to another idea and thus the face of food continues to change.
That being so, cookbooks by those talented (not necessarily famous) chefs are really just a snapshot of what is new at that moment in time. Ergo, there will always be a market (need?) for new cookbooks.
And long may it remain so.
Jock