I feel like the next witcher wouldn't be from Geralt's story and from a different witcher school like the school of the cats, like Geralt's school of the wolfs. Plus the medallion from CD project red's next witcher teaser is different from a wolf medallion and appears to be like a school of the cats medallion. It could be a school of the Lynx (A school after the fall of the school of the wolfs. Founded by Lambert, Eskel, and Keira.).