Yeah, but remember Xenonauts 2 already isn't a game you can complete in a couple of hours. If you're assuming that each mission takes only 15 mins (which is a bit of stretch once you get past the early missions) then that's still 8.75 hours for a campaign spent just on the tactical map. Realistically each campaign is an absolute minimum of 10 hours, and for a lot of people it's in the 15-20 hour region. It's already a long game, even if you win your first campaign - much longer than the first game was.
However once the mod tools are out I can almost guarantee someone will immediately make a longer and expanded version of the campaign and everyone will be happy. The type of people who like Long War are a pretty small subset of the people who buy these types of games, but they're hugely overrepresented in terms of the active community and people who are interested in making mods!