-Maybe he is in captivity that is why nobody can find him.
-Maybe in the next volume Ruby and her team will rescue him as a payback.
-Maybe it is like the The Wizard of Oz. Ruby just like Dorothy going to search and find wizard Oz(pin). I mean at the end of the season she started to walk on a long road, with 4 partner. Dorothy done exactly the same thing. And she (probably) killed Cinder = Wicked Witch of the East before her journey. So we've got one (main) witch left.
- So i'm pretty sure that Ozpin is alive.