To kick things off, Firaxis commissioned the clever folks who made the Long War mod for Enemy Unknown to produce three day-one mods for XCOM 2.
It also means we can expect anything from an increase in moustache variety to a revamped campaign or series of total conversions. Theoretically, that means someone will iron out the things that annoy you and build on the things you love. XCOM 2 isn't just a big pile of tactical brilliance, it's also a big mod-friendly pile of tactical brilliance.