It turns out, the answer is simple: the team feels like the the story of Ori is complete.
Thank you. Certain games series (Halo, CoD, and Battlefield) all had natural ending points where it was time for new stories, games, and different IPs. Larian has also figured this out by doing a handful of Divinity projects, then BG3, and is now focused on entirely different games unrelated to Divinity or BG. The ability to take risks is exactly what we need.
Though the lack of games from Valve drives me crazy, they are also the kings of not pissing a franchise into modern, wall-running mediocrity.