I think he will be instrumental in destroying Shaidar Haran. The issue with Fain and the Dark One is that they both represent aspects of the embodiment of evil in the world which restricts and corrupts the free will of the individual threads of the Pattern whereas the Creator, by choosing neutrality and creating forces that are neither wholly for good or for evil, has allowed free will to coexist with the Pattern. I think RJ meant for the story arc to result in absolute evil destroying itself, so that the only thing left would be petty evil to balance with petty good.