Bob Greenblatt is the new entertainment chairman of WarnerMedia. As such, he’s inherited HBO’s crown jewel, “Game of Thrones,” just as it begins its end. Now the question is, where does he want it to end? According to SFGate and The Wrap, the long-running fantasy series will premiere its eighth and final season this April. And the currently untitled “GoT” prequel pilot will begin production in early summer. But Greenblatt doesn’t know if doing one spinoff will work, much less two…or five!