You can just as well turn it around: did they inform customers when they would stop supporting their application?

When the next version of macOS comes out and whether it will bring significant breaking changes is not within their control though.

Well they know a new one comes out every year so they would have to be willfully ignorant to not know that and that it have a chance of breaking behavior.

If they want to charge for new versions it would only be fair if they at sales time gave a time range for how long they were going to support current versions.

Some releases are much more substantial than others though. Apple may even deprecate functionality they depend on without a suitable replacement. It doesn’t seem unreasonable that the customer is given the choice to pay for the upgrade or not, rather than build in the insurance cost all the time.

I think the programmer is much better equipped to make a informed choice about this than the customer.