https://steamcommunity.com/app/362490/discussions/0/364040166677494413/#p1
"The focus of the next update is a huge new map for story mode, it's at least as big again as half of the current game, and everything in it is new. There's quite a few important new features and a lot of very nice improvements to graphics and animation in general. We've also just hired 2 new artists and made some great productivity enhancements to our level design tools.
Arena is only getting a few new items for now, but we'll do an arena update soon after this one (really this time!) and add some nice new features there too.
This is one of the very few remaining story maps that doesn't require the same functionality as the outdoor content for the arena. We've been working on that too, and once this update is out completing it will be a top priority."
I guess it's kind of vague, but it sounds like there will be a lot to do on the new map.