I may have missed the notice, but the latest information I have seen is that High Sierra is the latest Mac OS that Wolfram officially supports. I installed Mojave on my laptop and it seems to work, although I do get occasional notifications that Mathematica is not optimized (rather than the one-time notification that occurred with High Sierra).

The first question I have is whether Mathematica under Mojave is supported by Wolfram. The next question is when will a 64 bit front end be released. I am concerned that when the next version of the Mac OS is released there is no guarantee that any 32 bit code will have a chance of working.