I expect someday it will come. That would only make sense, and it most likely will be an "expansion"... pyandonea is reputedly roughly the size of vvardenfell, and it would make great sense for them to refit some underwater experiences with that one as well, because sea elf and all that...

Plot-wise it may not fit all that well into the current story, but that would actually work for an optional expansion - have a story just for them! Possibly involving some new threat... or a very old one (sload, perhaps?)

The question would be, when. I would think they might spend some time filling out the map we have before going there... one DLC at a time!

...what I would hope for before we get that one though would be Maormer as crown store optional race, like imperials!