Update on 2018-06-19: We have found a new maintainer (Ralf Stubner), and the Github repo has been transferred to https://github.com/daqana/tikzDevice.
Today the tikzDevice package was orphaned on CRAN, mainly because neither Kirill Müller nor I have time to maintain it (both of us have other priorities). I still love the fact that it makes it possible to write native LaTeX expressions in R plots and generate high-quality PDF. I still think it has the most appealing PDF vignette among all R packages I have seen.
If anyone has time, understands C, and loves TikZ, please feel free to take over the maintainership. Since the package has been orphaned, you won’t need to ask for our permission to take it over. I’ll be happy to give you write access to the Github repo yihui/tikzDevice, or simply transfer this repo to you.