While I do prefer Python over R, the idea that R will just "die" simply because it isn't as popular as Python is ridiculous. There is a very large user base, good ecosystem of tools, many talented people actively developing in/for R - it's a great tool for so many purposes and it doesn't seem to be going anywhere.

Also, which languages have been truly popular historically and then died? Only Pascal comes to mind. (I'm sure someone can correct me on this.)