It has been hinted at in the past but now we're starting to see solid notice from Apple that it is dropping support for 32-bit macOS programs in the near future. While I can see how this makes sense in the walled garden of iOS, the macOS / OS X environment has always been a bit more flexible in that you could run older software.
We dealt with this when Apple dropped PowerPC and Rosetta, but the change of CPU architecture was a bit more obvious since it was apples-to-oranges. However, the difference here is that our x86_64 platforms can still natively run 32-bit x86 code. It is simply a decision by Apple to cut off 32-bit code. Sure, it is great to get rid of old stuff but it also cuts off useful software which might not be maintained anymore.
I'm curious what benefit actually comes from dropping support for 32-bit software. Is there any measurable performance gain that we would see from there no longer being support for 32-bit apps running next to 64-bit ones? Or is it simply that Apple doesn't want to maintain the 32-bit APIs and support libraries anymore and this is simply cleaning house?