You also make a good point. I didn't go into too much detail about ReasonML in another comment, but I know Jordan (@jordwalke) has plans for a ReasonML v4 [1] with slight syntax improvements. I don't currently know the status of that work, however, but I think we'll want to make progress soon.
So the TL;DR is more that ReasonML is not going anywhere, especially since Ahrefs have a huge ReasonML frontend codebase [2].