This is expected to advance to phase 4 at the same time as GC. Most of the work is happening in the GC repo, so I would track progress over there. Everyone is also welcome to join the W3C community group here then fill out this form to join the biweekly GC subgroup meetings.
I'd like to start a conversation around the state of this proposal and what steps are missing to bring it to Phase 4.
This is inspired by https://github.com/WebAssembly/tail-call/issues/15, which (seems to me) helped to focus the work of multiple actors towards making progress.