i stopped using R a number of years ago because it is not useful for very large datasets (in the tens to hundreds of millions) and now use kdb almost exclusively.
R has quite a few specialized libs to deal with large datasets (out of memory). Nothing keeps you from hosting the data in a DBMS and using SQL (or dplyr) to pull the data in an appropriate format.
I run a data science department at a corporation and this is exactly how we handle our massive amounts of data. It's rare that we're using a billion+ data points in one model so we use SQL to get the data we need in the format we need and move forward from there in R.