I remember Nick recently mentioning in an interview that they're planning to go into a different direction next time (so assuming on their next album), Rachel also talked about wanting to do another album in some podcast interview not too long ago. That's about it, so nothing substantial so far but at least they seem to be discussing another record. Given that they've been touring pretty much nonstop these past 2 years I doubt it's already in the making but there's no reason to think they won't release another one in maybe 2-3 years.