Once they activate the Brizy PRO license (with the Item Purchase Code from the marketplace they purchased your theme from) they'll get lifetime updates for the PRO.
This is independent on your decision to renew your author license or not. If your author license was active at the moment they activated their PRO license, they'll get lifetime updates.
The license they get will not include the premium design that Brizy PRO usually comes with. If they want to unlock the PRO premium design assets (blocks, layouts, icon packs) they'll need to purchase a separate regular license from our website.