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.
