the only problem with having new dungeons is that the older ones become unused. True, as I am also quite sick of the current three primals, reusing content is a little frowned upon. However, if events caused you to go back into some of the older dungeons to open a new wing or area that wasn't available before with a new set of bosses would that be so bad? I personally don't mind hard mode...but extreme mode really just feels like "omg we must give them more stuff to do."

I would think that the arrival of a new primal, say leviathan, would cause power shifts in the beastmen tribes and cause surrounding areas to be affected...sadly all of this thread is very hypothetical even if we can clearly see how areas can be used for future dungeons and story arcs. Just look at world of "not to be spoken of ever on this forum" and how there were zones from vanilla that had no purpose until several expansions later.