Another important metric is the use of R in clinical studies. The FDA now accepts much research in R whereas before they did not. That is a slow moving change, and shows R will be around, at least in use by Pharma, for a while.
The best thing that can happen to R would be to rewrite the parser in Haskell and make R a domain specific language. Leave the stats/R language to statisticians who originally designed R, and bring in the Comp Sci crowd to actually make a meaningful speedup.