I would oppose a blanket migration of all question with a LaTeX tag.
The R statistical programming language includes both Sweave and knitr, which are reproducible research tools that allow for the embedding of R code within a LaTeX document. Questions on these topics regularly come up.
Those of us following the [r] tag often flag those questions to be migrated to tex.stackexchange.com when the answer is likely to involve only LaTeX. However, sometimes the solution involves a mix of the two (LaTeX + R code) or just R code.
Also, there are questions within the [r] tag that are about tools for exporting R output into LaTeX, that, again, are purely about the R language. (Like the xtable package or some functions in the HMisc package.)
Again, we try to be good about migrating questions where the solution will involve only LaTeX, but it is a useful tag to have around (for some).