Farmers, fletchers and shepherds all have the same cloak (brown with no apron), so I imagine cartographers will share librarian traits and also have a white tunic. But I don't think they're just going to drop into the towns of your Realms world that you've already explored, they'll only appear in new villages in unexplored areas (or they may appear when you breed villagers). Same for the Woodland Mansions, they'll most likely appear in wooded areas that you haven't yet explored.
I guess the 20-dollar question is this: Will cartographer maps point to areas in pre-1.11 worlds where a Woodland Mansion would have spawned if that area hadn't already been explored? It would be a rip-off to get a treasure map that points to your old cow barn, lol.