It's really easy, for one, by the end of this series do you think they'll truly kill off the galrans once Lotor is defeated? Varkon, Kolivan, Thace, Acxa, they're showing us that there are good galrans, as we get further in the series they might introduce galrans who are beginning to doubt themselves and their own motives. Once Lotor is gone, they're going to need a new leader, or not even a leader even, just someone to follow or look up to, Keith. I could see it being Keith. Keith who would have experience over being a galra and being a leader, who knows how galrans think, and why they think the way they do. Who will literally remind Allura of how her father treated the Alteans, Keith will grow into a fine ass leader who will make Shiro proud, the leader who Shiro always believed in, the leader who Steven yeun said will surpass Shiro. This is just a theory I've been having for some time, you don't have to believe in it or anything.