I checked some of the engine/tool issue trackers and couldn't find any clear signal on what the status of the proposal is when it comes to stage 3 implementations. What I found so far:

• Babel: v7.19.0 (blog post). Babel is actively working on aligning with the latest revision, see Add 2022-03 decorators version (stage 3) babel/babel#14836.
• TypeScript: v5.0.0 (blog); metadata in v5.2.0 (blog).
• esbuild: v0.21.0; metadata in v0.21.3
• V8 has started work on accessors and decorators.
• Spidermonkey is (somwhat?) actively working on it.
• I couldn't find a signal from WebKit/JSC though I might have looked in the wrong place(s). @trusktr created https://bugs.webkit.org/show_bug.cgi?id=277593 which may be the most canonical bug.

Does that reflect the current status?