Does anyone know if a change in IGN will automatically update that players trade shops with the new name?
Player shops don't always but private shops do by opening them. It has been known that Trade shops can work this way too. I believe Emerald has experienced this recently can give some intel on the situation
Can confirm that the old name in privated shops will update automatically or once you click on one chest they will all update at once. Privated chests/shulkers will remain with your old IGN, until you open that chest/shulker and it will manually update. [Edit] I BELIEVE Items with private signs (like beacons) however, will not update your name and you would need a moderator to break those. However, Hope that helps