Ok, since you guys mentioned Male and Female versions of the Archfiend and Dragonfiend Rider, I think I can guess that one of those two will be an evolution of some sort for the Void Incarnates. It just seems like a logical possibility to me...

We've also seen some weapons in the DNs to go along with the Archfiend. It is possible that there could be a few variants. But on the other hand, those are a lot of weapons which means a lot of variants. Honestly, I don't think there will be many variants if there are going to be some. My second guess is that some weapons, like the sword, will be its own possessable character, just like the Overfiend Blade. That would be quite fun to have, IMO.