This is really not looking good for the Master. I can either see it ending up with him dying, and the brother and sister having to venture out and train themselves, or him living thanks to the sisters mysterious power after losing the fight and being on the verge of death. In the second scenario though it would make the sister kind of a deus ex machina and I feel like she would have to be removed from the story for a while (such as being kidnapped for her power) and during that time the broken Master would train the brother... Really though I could think of thousands of scenarios so it really doesn't matter because I won't be right anyway.
I'm enjoying that this series is keeping me guessing.