I'll need to fact check this, but doesn't Murphy has as many bad movies as Hart?
daddy day care
tower heist
vampire in brooklyn to name a few
Like others have already said, there's already a future Kevin Hart waiting to take Hart's place, if he's starts slipping.
Also ain't there like a 1 famous black guy per half-decade rule?
Hart's already said he expects the movies, etc to go away hence his Hartbeat productions company.
I don't see how Hart could become Sandler, given he's already produced specials for Lil Rel and Keith Robinson.
I've not seen their newer hours, but I've seen lots of quality material from both of those guys.