I'm fine with any setting as long as the story is good, but personally I'd want to see something we've never really seen before.
Right now we have the Azem Key in our posession, and it would be a shame not to use it somehow. It's like a Chekhov's gun that we've waited for to go off since 7.0.

On the other hand, I really miss Eorzea and would like to see all the characters we know and love again.