Next expansion, I'm thinking either a portalled otherworldly place, the emerald dream, or possibly deep underground, to the tomb of sargeras? But the whole thing underground would get boring, already done Vash'jir and Deepholme. Got to be chasing the legion to another world I reckon.
A retcon of ANOTHER continent would not work for me, unless it was really really well explained. Could the cataclysm have formed a new landmass?