My mother certainly moved on to cards, as you say, but also onto paint pouring and other more colourful activities - I think this was an outgrowth of stamping, with all the ink mixing techniques that entails. Wouldn't be surprised if she moves into marbling or similar soon

Yes, I can see that. Paint pouring has longer legs than other fads but I think it will peter out eventually but everyone can just repurpose their loose acrylic paint for the next thing, there really won’t be an acrylic contraction.