It is extremely unlikely that the Grimvale questline ended with Paradise Lost (Oskayaat) and I assume this is why the Quest Log is not complete. This is a theme with ample possibilities for continuation and something that Cipsoft can revisit whenever it needs to fill some gap in the creation of future quests.
In general, the Lycanthrope class includes mammals (Bear, Boar, Wolf, Fox, Hyena, Tiger, Lion, Badger and Panther) but in Paradise Lost we had a creature that hatches from eggs (Crocodile). Most of these creatures are predators but there are exceptions like Boar and Badger.
Taking this into account, the variables and possibilities for new Were-Creatures are huge, to name a few: Polar Bear, Winter Wolf, Skunk, Panda, Elephant, Mammoth, Gnarlhound, Horse, Buffalo, Clomp, Parder and others. I assume at some point we will have a Were-Creature focus in Svargrond (to address ice-related creatures). Furthermore the Lycanthrope's curse can address completely new events with animals that may not yet have been added to Tibia's lore.
So summarizing the idea, I believe that it even has an ending planned. Let's assume the Were theme is covered every 3-4 updates, then there would be plenty of possibilities available to work on in 10 years or so. Sometimes Cipsoft likes to release information about future updates through Quest Log, books, NPC talks and stuff like that. For example, when the Ancient Feud ended, the players' quest log released information such as that the curse had reached the jungle of Tiquanda, which would make it easy to assume that Tigers and Panthers would be a high possibility of new Were-Creatures in the new chapter of Grimvale Quest.