There a few patterns I have observed in the vintage car parts industry, depending on the demand for the parts (tied to collector demand for the cars). I'm sure these apply to other industries like the Atari guy.

Consistent demand, med-high value: the business' inventory is bought up by a larger business that supplies a related niche as part of an expansion plan. This can result in poorer availability/service as the tribal knowledge of inventory organization and item details is lost in transition.

High value but demand is inconsistent/slow: parts bought up by a collector or restorer, they go off the market into storage in order to keep a specific collection going. They may in theory sell parts to others but usually difficult to deal with and almost always requires an "in".

Low demand low value: Scrapped, or stored in indifferent conditions (outside or piled up in storage units) until everything degrades.

Of course, if another "that guy" appears there is a possibility for a stable transition. But as other commenters alluded to, these folks tend to have idiosyncratic personalities and lifestyles so that happens very rarely in my experience.

You're SOL unless someone else decides to take up the mantle of the last guy. So basically every 90's comic book reboot, except they turn into a jaded parts guy instead of jaded super hero.