You may be interested in knowing that about two years ago, a team of engineers at Dropbox wrote gory details about their use of Rust and it was inspiring. The passion about their work really came through. The team also held an AMA on /r/rust that went well. See here: https://www.reddit.com/r/rust/comments/fjt4q3/rewriting_the_...
It might be a couple of months. The open sourcing of Cloudflare workers was announced in May and still has not been released. [1]
I think you should remove the part about closed door development as a negative for nginx given the way that this has been developed.
Why? It's closed door development in nginx from their perspective. This doesn't apply for their in-house project. They not telling you why you would want to switch off Nginx, they are telling you why they've switched.