So with Kabuto powering up and implying that he has surpassed Orochimaru, I guess the chances for theories of his late master coming back from the grave becomes even slimmer.
This latest chapter is a surprise, because very few would expect Kabuto to be that powerful. Sneaky, yes. But powerful enough to take on an Uchiha, well, I had my doubts then. But now it looks like the only ocular jutsu he's wary of is the rinnegan, which both brothers do not possess. I say this because when Tobi asked him how to stop the edo tensei, Kabuto thought to himself that he could not fight against the Rinnegan that time (page 7, Chapter 520 - "The Secret Behind the Edo Tensei").
But if the Uchiha siblings decide to use Amaterasu, I think Kabuto will be done for. Still, that's unlikely to happen because, their objective is to capture him alive so that the edo tensei may be put to an end.