Won't AI art become (as it already is to quite a degree) the opposite of "off the rack". It can become as bespoke as you want, and increasingly so as the technology matures. And it'll surely be far more versatile (not to mention fast and cheap) as any individual artist could be.

But traditional, hand-produced art will presumably continue to hold its value, and there might remain a collector's market for new pieces.

And, something that's often overlooked for some reason, hand-made pieces from non-famous, local type artists will surely continue to sell for quite some time, because they're hand-made.