Here's the latest Mastodon development roadmap: https://blog.joinmastodon.org/2021/12/roadmap/
Some interesting stuff in here, like reply controls, dynamic roles, and groups potentially replacing (or only supplementing?) the local timeline. Seems like some items have already been implemented in v4, though—like batch filter rules and post editing.
@lrhodes I read it as groups behave more like a local timeline. Not that local TLs become groups