Nothing so far has hinted at Meracydia, and Yoshi P. did reveal his desire awhile back for another winter-themed expansion ala Heavensward. The hints dropped in 7.3 seem to make me believe we are headed North, and will explore the areas around Garlemald still clouded over. If not that, we absolutely are utilizing the key and hopping to another shard for Shadowbringers the Sequel.