I still have to manage my first playthrough in Xenonauts. I bought it recentry with Humblebundle, just before I played X-Com EU/EW, which was a sad experience because I liked the game, but hated the bugs. Another squad unit game I played recently was the Shadowrun Returns game, which I liked very much, too, but it was too short and maybe I played it on a too easy difficulty.
Xenonauts is great and I really love the 2D isometric combat. It is clear, I can see everything. I would like more to have a good 2D engine than a 3D engine where I lose oversight. (I didn't like X-Com for that matter, I always missed a wall or an opening and got surprised by enemy Forces. I never got when a wall is visible or transparent.) If you get a 3D engine done which feels like 2D isometric, that would be perfect. Important Thing for me would be that you can not only see some tiles like in other squad unit games, but a huge field like in Xenonauts.
As I understand, your next game will be squad unit combat, but not necessarily Xenonauts 2? So I have to be honest, I don't need to have another Alien defence Simulation if you can make another tactical squad unit game with another Story. I really would like some SWAT game in New York, for example. Or Shooting Aliens in Cardiff. (How great would be a Torchwood licence for a squad unit game? Rhetorical question.)