I have strong doubts that partial application will ever advance from stage 1. The reason is that partial application was supposed to compliment the pipeline operator[1].

    value |> fn(?, "static string")

However earlier this month they advanced a version of the pipeline operator with a definite topic marker which makes partial application useless in the RHS of the pipeline operator. This was of course really controversial, as you can see if you read thought the most resent issues (particularly the closed ones).

https://github.com/tc39/proposal-pipeline-operator