I guess it depends a little on what Poppins is. If it's a more souped-up carousel with a nicer queue, for example, I'm not sure the trade-off would be worth it for me. If we get a good rather than mediocre dark ride, maybe it would be a reasonable trade-off.
It also comes down a little to preference. Mary Poppins is one of my favourite Disney films, but it would have made me very happy to see Coco in the parks in some permanent way as I liked the film so much and, otherwise, Disney is likely to forget it ever existed as far as the parks are concerned.