I feel like the #1 thing they ought to be doing is opening it up as a platform.
I think their original mission was: build a better keyring. They've done that, it works great! But the idea that they will follow that up by building a chat app better than Slack or Teams seems like hubris, akin to trying to win two roulette spins in a row.
If, OTOH, they opened up KB as a platform, I'm not sure what exactly would happen, but it could be pretty cool. It's not hard to imagine, say, a distributed social media app built on exposing a feed of files your KB friends have posted in their public KBFS, or indie game devs using Keybase as a cheap and fast way to add authentication and in-game chat to their games. I'm not sure how they would monetize that exactly, but it seems like a better problem to have than "let's beat Slack and Teams with five developers and a several-years-late-start".