Yes, from briefly looking at the Rpy2 documentation there are some precompiled binaries. If you’re using Windows, you’re not going to be able to use this package in Slicer’s environment at this time. I recommend using pure python packages when using Slicer on Windows.
From the other thread that you linked above, the important information is in JC’s comment.
Second, on linux (and most likely macOS), it is indeed possible to pip install official packages (even the including binaries like
scipy,tensorflow, …).On windows, it will currently work only for pure python wheels because the official package for python 2.7 are built with a compiler than the one used for the official wheels. Note that this will change as soon as we standardize on Visual Studio 2015 and switch to python >= 3.5.
The work towards python3 I believe is scheduled following a 4.10.1 release. So likely early next year.