There is a lot of history and philosophy packed into that question, Peter!
Is R an interactive, easily extendable, capable of being goosed through Rcpp and kin, functional programming language that has its greatest application in exploratory data analysis and prototyping? (One view of the status quo.)
Alternatively, should it head in the direction of being dominantly compiled language with a sort of macro level of user extensibility that is destined to be a great engine of Big Data Real Time Streaming types of problems?
In a world that I will probably never see, the functional interpreted R will be translated into the functional compiled Haskell.
Why is this my vision? Imperator/proceduralist programmers often find implementing an R toolchain something of a PITA. Maybe that's why so many shops turn to Python, which has the same paradigm as the mainline languages.
If the world of data engineers were more richly populated by afficionados of functional programming languages like Haskell, they would adore R. And, in theory at least, R would adore them, because a program that compiles in Haskell is said to be "self-proving" mathematically and logically. (I take this on faith.)
I see a world where R{base} has a Hackage library ready to import, soon followed by tidyverse and the other must haves, and eventually the entire CRANsphere. functional-to-functional
And maybe I've got a winning PowerBall ticket in my pocket somewhere.