Why would it lower the value of being a Hollywood mega superstar?
If anything wouldn't it increase the value of being one? Because now Megastar Jim Bob Jones or whoever can "appear" in hundreds of movies a year and collect checks from all of them for using their likeness. Instead of those roles going to smaller actors who would presumably get the part today.
Also it makes the value of that mega superstar more valuable because their deepfake won't age nor will it be encumbered by their death. We could start seeing Marilyn Monroe in movies again. And if you're someone like Brad Pitt, it means suddenly you have an entirely new revenue stream from licensing your likeness for years, decade, etc.