This is something I've been thinking about in the last few days. whoever played Xenoblade Chronicles X will tell you that the world is amazing, but it feels somewhat empty. So why not improving that with the next game from Monolith ? it's clear that the world won't be considered small by any mean by the time the next game releases and, even if it was, they could still add new regions/nearby planets to explore. What Monolith would have to do is to upscale Mira instead of working on a whole new world, so that they can release their next game sooner than in 5 years and cutting costs on it's development. 

Of course Mira would be now filled with new cities and environment changes would have happened since the time X takes place, meaning that the game won't feel  the same to those who played X before, also it could be a nice thing for them to pick up the game to visit areas they never saw in their original playtrough and of course a totally new plot !

Note: I haven't played Xenoblade Chronicles X neither I know anything about the story so I don't know if something major happens to Mira during it but even if that was the case it doesn't chage much: many Nintendo games have different timelines/multiverses so if let's say Mira explodes by the end of X, this hypotetical game might take place in another universe where the explosion of Mira didn't happen/was prevented.

I don't mind a sequel to Xenoblade Chronicles X. I would like to know what the mystery around Mira is, but it needs to be in the vein of the original Xenoblade. The story presentation of X is unacceptable. In addition, the hundreds of ridiculous and boring side quests need to be eliminated.

It's an interesting idea that successive games would just expand a pre-existing world. Kinda like an MMO. I don't see it happening though. They'll just make a new game. People like new stuff. If you build on what already exists, you're by definition narrowing your potential audience.

I dont know how to add quotes from your original post.

you state that everyone will tell you XenoBlade X feels empty, and then later in your post you then say you've never played it. Please dont post something as fact if you haven't experienced the game yourself. It is not empty to me, its exactly in fitting with the game environment and if you played the game, which I really recommend you do :)

I really hope they move on to another game and environment for their next game, Mira doesn't need expanding upon and would be a lot of work still to make and be creatively limiting to some degree as they need to adhere to what has gone before in XCX. Also will limit potential gamers who didn't play XCX.

To quote click the "Quote button" under the comment you want to quote, you'll be re-directed to the reply page with the quote in your text box...

I didn't post is as fact, I posted it as result of what other Nintendo fans have been saying since December 4th.

I don't see how a next Xenoblade game featuring Mira could limit potential gamers who didn't play XCX, if anything it could give those who didn't purchase it the possibility to visit such an amazing world...

New project. Get the absolute fuck out of Mira. Seriously. Don't even resolve the plot. It wasn't good anyway.

Oh, and I did play XCX. It absolutely was empty.

I don't get it, you claim the world is empty but you haven't even played it?
Trust me, after 110h, the game is far from empty. I don't know what people was expecting, but for me a world that feels like you are on a Madonna or U2 concert, where you can't easily move, and you have to push people everytime you need to go to the bathroom is not fun at all xD.
Let me move freely, avoid the enemies if I want to or attack them. There are some parts where you can't easily avoid a battle because you are constantly being chased by different enemies, it's fun for some parts but not the whole planet.

Working on Mira for a sequel would be like dlc. If it's essentially the same planet but with more enemies and some new continents that would be like an expansion. I rather they create something new than to do that. But, I wouldn't mind if you could travel through space and visit different planets and Mira was one of them.

My ideal sequel would have more smaller continents but with very different landscapes, enemies, vegetation etc. Xenoblade wii was incredible in that matter, it had so many different areas that made the game more rich.
Xenoblade X is impressive, but for me it lacks that, more variety, more hidden stuff like caves, unexplored areas, special locations etc.

Sounds more likely it will be a new project to me - http://mynintendonews.com/2015/12/16/monolith-softs-next-project-will-look-and-feel-pretty-differen/

“I tend to get bored with things pretty easily, so I’d like to keep creating things with different approaches every time,” says Takahashi. “Along those lines, I’d definitely like my next project to look and feel pretty different from this one. The ‘Xeno’ name, by the way, really just exists to make it clear that these are Tetsuya Takahashi productions.”

Can't really comment on weather I would prefer a new project or continuation of Mira as I'm only just an hour in to XCX, May add my opinion in the future if I remember :)

He needs to resolve the Xenoblade X story line. I don't care if he does it in a massive DLC. I'd buy it day 1. And I think its a silly thought to say its a empty world.

Story was trash imo