I joined the 2019 beta program and initiated the install. The scroll down in step 2 says that the Fortran 18.0 integration in VS has been detected and will be removed if 2019 beta is integrated into VS. I went no further. Is that actually true? I'm running VS 2017 with Fortran 18.02 integrated.
Yes, it is true - and this is the same as every previous version. There can be only one version's integration in any given Visual Studio. However, if you had previous COMPILER versions installed, you can still use the previous two versions (if they supported that VS version.) See https://software.intel.com/en-us/articles/using-older-intel-visual-fortran-versions-in-different-microsoft-visual-studio-versions for more info.
Thanks Steve -- I had (erroneously) thought that allowing multiple compiler installations implied multiple Parallel Studio integrations. The link you supplied makes it clear.