it's Apple making their new OS 64 bit only.
This was promised in 2011 and was supposed to have happened with Yosemite but Apple kicked the can another 5 years.

It's now really real with the release scheduled for Sept. 10.
Me too! I don’t want to update from Mojave. It works just fine.

Then don't.
I would just like to use the DAW plugin, and some new real tracks would be handy. Can PG not have a .version for those that are not going to update to Catalina?

Why do you think that a 64 bit only version will not run in Mojave?

64 bit only apps have been real for many years. Some run in Snow Leopard.
BIAB 2020 Audiophile iMac Pro 4TB 128GB SSDx2 Catalina; 2012 MBP Catalina
Overture 5 DP 10 LogicProX Finale 26, Encore 5.0.7 SmartScoreX2P Notion 6
Legacy G4-1K DP OS 10.4.11 / OS 9.2 Apps