I’m not so sure they’re worried about apps breaking. They’ve certainly stuck to the “no more 32bit iOS apps” thing.

Apple can get away with that on iOS, but they're a lot more conservative with macOS.

To expand on your example, I maintain a legacy app that is stuck in 32-bit land because it relies on the QuickTime framework. QuickTime has been deprecated for seven years, and the transition to 64-bit has been in progress for over a decade, and yet my legacy app runs just fine even under the Mojave beta. There are multiple time bombs lurking in that app, and one of these days I'm going to have to rewrite it from the ground up, but I've been astonished at how long it has lasted.

Apple knows it would be bad karma to make a large number of legacy apps and games suddenly break on the Mac. They're not idiots; they have a perfectly good idea of the scale of mutiny that would ensue. So I'll eat my hat if OpenGL doesn't continue to work for at least the better part of the next decade.

They said in the Platform State of the Union that Mojave will be the last macOS that runs 32bit apps, so QuickTime.framework and your app are running out of time!

Huzzah! Thanks for the heads-up. I’m looking forward to catching up on the whole SOTU.

They specifically mentioned QuickTime in the release notes as well.

> QuickTime has been deprecated for seven years,

It has entirely been removed from the latest (since 10.12 IIRC?) SDKs so now you have to keep older SDKs just to build your app.

True — 10.12 is my recollection as well — but I’ve been bitten so many times by compiling under a new SDK, especially with an older build target, that I do that as a matter of course anyway.

I find it hard to fathom that people think a huge software company like Apple doesn’t have awareness of the impact of its changes or people responsible for compatibility.