Just recently BS once again confirmed that most important things will be resolved in the plot, except for a few smaller mysteries and those things that will come in the outrigger novels (e.g. the conflict in Seanchan). Therefore I think Fain, who was an important character since book 1, will be dealt with in the main books.

I don't see how Fain could defeat a pack of 50 Super DH and Slayer; and think such a scene would be a kickass end for Fain.