To be fair, visiting other worlds has been a plot point in numerous Final Fantasy titles. I'm fairly certain that we'll be exploring more of the Source in the future, though I wouldn't be opposed to visiting other Shards so long as the story told is an engaging one.

The Void, in particular, is of great interest to me. I quite like the aesthetics involved and would love to see more. As a plot point, finding a way to fix it would be of benefit to multiple individuals which further makes it worthy of a potential expansion premise.