It they want to follow Legion footsteps - releasing 8.X big patch with outdoor content/dungeon (and raid assets, so whole raid can be tuned during 8.X.5 PTR) and later smaller 8.X.5 patch with 'evergreen' content and raid - next patch has to have some content. It's too soon for new zone in my opinion, but they need to make storyline leading to Azshara and create/revamp dungeon.