I do not think anyone who has an "orphan" is out of luck. It complicates getting proprietary parts and technical advice, but so far I am not aware of anybody owning any brand that was not able to resolve a problem.

I suspect as coaches get more complex and contain sophisticated componentry problem solution will also get more difficult, but not impossible.

There are a lot of coaches whose converters are no longer in business or supporting the product. I doubt if any are sitting up on blocks on the front lawn because they are not driveable. (Unless they are from TN, in which case that's how we park all our vehicles.)