I wonder if the witches losing their power due to the loss of Elf Island has to do with the chains binding the Beast breaking. Personally I don't think Guts will use a behelit or succumb to the Beast's temptation. The big difference between Guts and Griffith has always been that Guts wants to earn his power and victories with his own two hands, whereas Griffith will snatch at power regardless of the cost or where it's coming from. Guts has already seen where Griffith's choices lead to and has rejected that method, he's not going to choose that path now just to become an inferior version of Femto. Or at least I hope not.
