Going into space doesn't really seem like a proper setting for FF14 at the moment, but if we start delving more into the Garlean empire and actually exploring their territory in-game, utilizing their technology, etc., then I could possibly see it happening. It'd just need a good transition from the midly steampunk/pioneer-ish level we've seen so far, in my opinion.

Now, on the other hand, I'd LOVE to see some surrealism stages, like FF9's Memoria, or inside the crystal in FF12, etc. Those kinds of areas were always very memorable and unique, and the developers could go nuts with them... but again, there'd need to be some good transitions storyline-wise.