The proposal is stuck at stage 3. AFAIK, to proceed to stage 4, it needs two independent implementations, but Firefox [0] and Chromium [1] didn't see any progress in this area for about a year. Personally, after working with Angular for many years, that's not a language feature I am looking forward to.

[0] https://bugzilla.mozilla.org/show_bug.cgi?id=1781212

[1] https://issues.chromium.org/issues/42202709