I think the Medieval Blacksmith has given a pretty good indication that an expert level castle can sell well. The MMV and Joust sets were created over 10 years ago - that is an eternity ago when considering the current Lego market and offerings. After all, they’re now making 18+ sets consisting of flowers, character heads, and art.
As much as I’d love a full Castle theme, I know we’re not getting one without some kind of media connection ala Nexo Knights - which means for me at least, it won’t be what I’m looking for. Best chance is a license like LoTR to come back and give us some useful parts and inspiring sets. In the meantime, I’ll keep grabbing my 2-3 copies of Medieval Blacksmiths and 3 in 1 Creator sets and hitting up Bricks & Pieces to expand my armies/parts.
Let’s hope they keep this ball rolling with a castle inspired set here and there going forward...