I generally disagree with this sentiment. Castles in Germany is from this year, and we also have Über Stock und Stein and Star Wars coming out. We also have the Winter-Edition expansion in the Advent Calendar (which should be available on Cundco in the future, I believe). Yes, it would be nice to get another large expansion, but those have been less consistent in recent years. There was a four-year gap between Bridges, Castles & Bazaars and Hills & Sheep, which just released last year. I think they're sticking to their game, especially if you count any of the Carc2.0 products (which I don't, but it still takes time for them to update the graphics, rules, and packaging).
I imagine that Spielfest will reveal something new, but it won't be anything too big since there are already two spin-offs for this year. Maybe a new promo, maybe Dutch/French/Spanish castles or monasteries. Who knows?