Yes, if your only heuristic of 'falling behind' is 'not getting the latest OCaml features'. It turns out that even OCaml from a few years ago is perfectly usable to build an excellent JavaScript-focused compiler.
@dmit, we will have to agree to disagree there; the reality is, only a very few people are using the absolute latest OCaml features. If you look at the Opam package build matrix: http://check.ocamllabs.io/ ... most Opam packages are building against 4.02 to 4.05. And OCaml in 2020 is great but it's still not close to what we need for wider adoption in its chosen native compilation space. BuckleScript/Reason is a different strategy, which actually does seem to be working for that goal.
Monadic let syntax would be a big win (allows for async/await-like constructs) in Bucklescript, and inline variant records have been nice once or twice (I see reason newcomers at dojos do this naturally almost every time shortly after introducing variants).
Like I said, I know the tradeoffs between JSOO and Reason. And lack of features from the past 2~3 years of OCaml development is one of them.