If you have extensions that you installed from the Extension Warehouse and they are also available from our ExtensionStore, then you can simply install a version from our ExtensionStore.
Later on if there's an update the ExtensionStore dialog will tell you and you can install it that way.
The Extension Warehouse might also tell you when there's an update available from there - you can only prevent this by uninstalling it from the Extension Warehouse.
Where licensing is involved you need to stick with the hosting platform that handles it...