There's definitely some work to build atop the new functionality available in 5.0 and make sure there's plenty of good learning material.

In terms of the compiler and runtime development, the OCaml and ML Workshops at ICFP in October have videos that cover some of the experimental work happening: https://watch.ocaml.org/video-channels/ocaml2022/videos and https://www.youtube.com/playlist?list=PLyrlk8Xaylp7f8T7L5SFF...

There's also a compiler development newsletter that's posted on the discuss at regular intervals which details some of the other work happening: https://discuss.ocaml.org/t/ocaml-compiler-development-newsl...