As several people in the Stack Exchange article say, Mathematica 11.3 (and before) has a 64 bit kernel and a 32 bit front end. If you look at the builds that Stephen Wolfram uses in his live CEO-ing, you can see he uses version 12.0, which is 64 bit. How soon it will take for this to be ready is unknown, but it will almost certainly be this year.
My take is that it will be out before the next release of macOS is out,in the Fall.