i think only genetic issues associated with a morph can cause a morph to fall out of fashion.
champagne faces a double-hit: it causes the wobble we know from spider (also the super-form is lethal), and it is incompatible with spider, because champagne spider is lethal. Spider has the same issues, but really, if you have to decide between champagne and spider, if these two genes enter a duel..... its clear who will win. At the same time spider is taking a bit of a beating from pinstripe i think.
i think some people will continue with desert, because apart from the female fertility issues they are perfectly healthy. True you cannot breed females, but then, if noone just keeps BPs as pets and everyone breeds, that also couldnt work.
its hard to tell if one of the genes will ever really go away. Maybe the ones where we have many genes that basically do the same, but some are better than others? Im thinking of cinnamon and black pastel, where the super-forms have some issues, and mahogany and het red axanthic, where the supers are perfectly fine.