The biggest problem with most suggestions is that they're loaded with spoilers. Assume you're just starting out and you go to Empyreum. All that really spoils is that eventually Ishgard allows foreigners in. Kugane just spoils that there's *something* out east. Sharlayan would barely be a spoiler, since its mentioned as early as 2.0.

But what about the Crystarium? Other shards? And you can travel to one? Garlemald? So the war is over then. Don't even get me started on the moon.

I'll be very surprised if the next housing zone isn't Sharlayan or whatever we get in 7.0, if only because those are really the only viable options.