A drawback of the SQL is that it doesn’t provide first class functions, so (depending on the system) you are limited to those that are built-in or UDFs(User defined functions) that you can write and add. Functional Programming language makes it easy.
Even today, most developers get by without understanding concurrency. Many will just use an actor or reactive model to solve their problems. I think more devs will have to learn how to work with data at scale and that fact will drive them to FP.
We have seen lot of issues with Mapreduce. Already alternatives like spark for general use and storm for event stream processing, are gaining traction. FP is such a natural fit for the problems that any attempts to build big data systems without it will be handicapped and probably fail.