I don't see any posts about this. Tim Stamper posted this to Twitter yesterday. The keys have googely eyes and the mention of a vault implies returning to past projects.

Could this be our latest tease for a new Banjo game that ends up being nothing? lol

Started playing this on a whim whenever I had downtime and I got pulled in. I'm about 3 hours in so I'm guessing roughly halfway through the game and it's been a delight. Feels more similar to Kazooie than Tooie..like an actual collectathon that you can fully complete stages as you go (at least up to this point in my playthrough). It's a bit on the easier end but for a GBA game it offers pretty much what I'd want for short play sessions.