I won't say any more than they've released, which is that it's coming out in September 2018 and contains four new expansions for the game which can be added separately or combined together. The set includes four character cards, 18 adventure cards and 10 terrain cards.

Here's Osprey's blog post, and there's a little more artwork shown over at ICv2, where they mention Spanish conquistadors, a mysterious mountain, new companions, and a dark curse.

Once again I had the pleasure of creating the artwork for Peer Sylvester's excellent game - and I can't wait to play the expansions myself!