Upgrades are a cheaper way for pre-existing ACR users to upgrade their routine for the next expansion. If you already own the proper ACR and are eligible for the upgrade, you will only see the upgrade in the Minion store.

Not every ACR has an upgrade and whether or not they will have one will depend on multitude of factors. If you only see a ACR but no Upgrade on the store, that means either a cheaper upgrade does not exist or you are not eligible for it.