No multiplayer planned at the moment. But it is already possible to integrate maps/towns & scenarios from friends :)
I'm thinking about some coop support or that you can trade with other people, but that is sometihng after EA to decide if that fits the game & is fun.

Sounds nice. We need some kind of interaction - like trading or little expensive sabotage possibilities. Or somekind of coop - could be done by streaming to the coop-players like in rimworld mp-mod.