In taking on the series, Civilization creator Firaxis has shown reverence and understanding for what makes it special. XCOM's ingredients are hard to recombine: strategy with consequences. A technology metagame where you use the enemy's weapons against them. Emotional attachment to player-created soldiers and a feeling of meaningful death when you lose them. High-fidelity destructibility.
I can see a game where I have at least a dozen different objectives in my head at any one time, where I'm juggling a quantity of balls that any mainstream game would shy away from in commercial terror today. A game in which I both figuratively and literally create my own, unrepeatable path through, working through its tech-tree as my squad organically grows and tearing through the wall that lies between my soldier and the enemy.