I don't know about the rest of you guys but so far every time I finished a world I kind of wished there was more of it to explore. They all feel like the sort of universes that have a lot more depth than what's shown, as though I'm just scratching the surface... It would be very cool to go deeper into that with custom maps.
I'm not entirely sure what supporting user content in a UE4 game entails, but I am fairly sure that you don't have to release an entire map editor to do it, since the engine's got its own. It seems to have some form of user-content support built in from a quick look around Epic's launcher (which I already have installed for another project). 'Course there is still some work on the developer/publisher's part, even if it's just compiling the game assets in a way that mappers can use.

So are there any plans to support user-maps or other custom content?

That would be awesome

Custom maps, custom campaigns, heck let us create all sorts of crazy stuff. Full mod support will be perfect for this game. Especially in an era were most dev's seem to be waging war on mods.