For so long as Capitalism exists, the Witcher series will never be over.
Next think I know you'll try to convince me they are going to release five different versions of "Bladerunner" and start making Star Wars movies again, thirty years after the original trilogy ended!
I doubt that would ever happening. Though, they might try something new like a card game. Maybe with collectible cards, like that "Magic: The Gathering" card game from way back when. Before the turn of the century, right?
They could call it "Galaxy Wars: Enterprising New Trekkies". That would certainly get the attention of a lot of fan bases, I'm sure everyone would jump on that. It'd even have a pronounceable initialism.