XCOM's Long War mod [official site] is, to many, the definitive version of Firaxis' reboot of the alien-repelling strategy classic. As the title suggests, it extends the length of the campaign, making the fight against the invaders into a gruelling conflict rather than a streamlined series of missions. The campaign structure isn't the only thing the mod changes - it's like the biggest and most delicious expansion imaginable - and you can find all the details here, as well as download links.
Now, the team behind the mod have formed a studio and begun work on "a grand strategy game in which the player leads the defense of Earth during an alien invasion".
Typical behaviour, I say. XCOM: Enemy Unknown wasn't designed to be particularly mod-friendly and the clever Long War folks still managed to make one of the best mods of all time, and now that XCOM 2 has been designed from the ground-up with "a much deeper level of modding support", they're making an entirely new game instead of plumping for The Long War 2. I guess they enjoy a challenge.
The game goes by the name Terra Invicta and it's currently in "pre-Kickstarter development", though there's no word on a launch date for the crowdfunding campaign just yet. The designation "grand strategy" suggests this might be an even longer war and perhaps the tactical battles will be missing entirely? Going off the description on the official site, it sounds almost like a game of diplomacy rather than war:
An alien force has arrived in the far reaches of Solar System and begun probing Earth's defenses and building an invasion fleet. The player must assemble a council of scientists, politicians, military leaders and operatives who can unite Earth's squabbling nations with the ultimate goal of taking the fight to the aliens in the high ground of outer space.
With this and Stellaris on the horizon, grand strategy might be leaving history in the past and entering the space age. I'd like that, as long as I can still hop in my time machine from time to time and see how my crusader kings are faring, and whether the heart of iron still beats.