I don't think that either Taim or Logain are any of the forsaken. I think that it is very possible that Taim will be turned to the DO. After all, he is only in this for the glory and fame. He's said as much himself. Min had a viewing that Logain was destined for greatness. I think it is probable that her viewing would have showed if he were to do something evil. The position of Tamyrlin seems to be tradionally held by a man. Maybe this is the greatness Logain is destined for, after the last battle occurs and saidin has been cleansed. Yet another thought that occured to me. After Rand drives Callandor into the floor at the Stone of Tear, he talks about part of the prophecies that mention the one who will come after. Well, we already know that Logain is destined for greatness, could he not be that one? It would seem to support that hecould become tamyrlin.