Like huy-nguyen said, this is a tooling & ecosystem effort on top of OCaml ecosystem, and the language syntax is a small part of the effort. It's a bit scattered, but apart from ReasonReact, there is also https://reason-native.com/ and Esy that are parts of this bigger picture.
Both OCaml and Reason communities are also quite active in producing tooling and libraries, I'd suggest following the relevant forums. I believe Reason's development momentum is not centralized around a core Reason repo/org and a team.
However, one of the better things about Reason for me is that it is based on OCaml, which has been a rock-solid language for more than two decades. Its pace of evolution is quite measured - for example the algebraic effects work that has been happening is based on a formal academic foundation, and the implementation is often lead by researchers who wrote the actual papers.
The biggest issue I can imagine when a company adopts Reason is availability of bindings to Javascript libraries. In practice this has not been much an issue for me - once you get grips with the way bindings are done in BuckleScript, creating a binding is just another thing to do.
The other issue is significant upfront learning cost for the Typed functional paradigm. But it is the kind of fundamental learning that pays dividend for a long time, quite unlike learning libraries or frameworks that simply keep coming and going.
I find that Reason and Elm does solve for this constant library/framework trivia-treadmill of the Javascript ecosystem admirably, helping teams achieve enough technical expertise so they can effectively create most of the building blocks they need by themselves.
Plans for this feature morphed into support for OCaml's new programmable let binding syntax. With the PR above merged, you'll be able to write code such as
let.async users = getUsers();It makes the good stuff in OCaml more readily available to developers with different expectations such as syntax (JS) and package management (npm).
That Reason repo is just for the parser which is only one of the many pieces of infrastructure under the Reason umbrella (an important one though). Also follow BuckleScript, and esy for example.
But it seems it's catching up to TypeScript and left all its competitors behind. https://2019.stateofjs.com/javascript-flavors/