"Does the bottom fall out of that market someday when they no longer have the means of telling what's original or not?"
My guess is many 'Rolexperts' can not reliably tell a professionally prepared vintage 55xx, 1680, 1655 etc with a high grade properly aged replica case using a genuine movement, insert, and dial. When they find out they have ended up with one, you can bet they will (more than likely) get amnesia in a hurry and 'forget' it is not 100% proper.
(I know a bit about human nature, being part human.)
As for the bottom falling out of the market...the main thing to remember is the buyer sets the selling price, not the seller. Think about it.
When the buyers have had enough, the market will cool down and prices will fall. How much prices fall will depend on how fast and how far the market itself falls.
Meanwhile, some sellers will stick to their high prices trying to make a profit or get even. After a few years they are referred to as Watch Museum Curators.
I am a quartz Disney character watch Museum Curator myself.
Along with a 1948 Popeye watch like this one:
Picture from Collectors Weekly.