Exactly, a more sci-fi oriented XCX subseries, Takahashi could continue the story, continue to improve the Skell mechanics (gameplay, battle, etc.), they can also introduce another human group of refugees on another planet...
I am not really doubtful because they have two main studios, more than one hundred people, different development teams and close collaborations with other Nintendo's studios. In the same 2015 and 2016 years, they worked on XCX and Project X Zone 2 end developments and releases, they started XC2 work, they ported XC on 3DS, they worked on and co-developed Breath of the Wild.
With this new game, they want to create a more "Heroic-Fantasy" oriented Action-RPG ("true" real-time action battle contrary to XC games). I guess their work on Zelda Breath of the Wild (and earlier Skyward Sword), and the success of "Heroic-Fantasy" Action RPGs such as The Witcher 3, help to motivate them but they have surely original ideas too.