They could go with the hero route, or make scalable weapons, or let them share with another class for this particular content. Maybe we also just won't see another class, since we pretty much have most of it by now.. I would like them to actually add new specs to classes rather than diluting the ideas of existing classes even more..
They will have to figure out what to do about the artifacts after this expansion as well. So there is always a chance that they'll just remove all the necessary elements after that point. Imho that is the way more interesting question, how exactly will they handle artifacts after this expansion?