To coincide with the work people are doing on 64 bit Windows builds of Pd, it looks as though Apple is stepping up it's move toward 64 bit only in the next version of macOS: https://www.macrumors.com/2018/01/24/macos-high-sierra-32-bit-app-warning/

We've had 64 bit macOS Pd builds for a long time now, but now we need 64 bit external builds on deken to go with it. This will also likely mean that Pd-extended will no longer run on macOS 10.14 next year.