Pro desktop users represent just a fraction of a fraction of Apple’s business, but they’re nevertheless vitally important. They do much of the development that attracts people to Apple’s platforms and keeps them there, and they’re some of the company’s biggest evangelists.
The April meeting got things started by telling those customers that Apple was at least aware of their complaints and working to fix them. Announcing the iMac Pro in June in front of an audience of many of those users buys Apple some time and earns it at least a couple of positive conversations on the Accidental Tech Podcast; actually releasing it in December satisfies some of the pent-up demand for a pro-level system and bridges the gap between now and whenever the new Mac Pro is announced (and I wouldn’t be surprised at all to see a similar gap between the announcement and release there, either).
Everyone knows that the Mac Pro was a terrible blunder, including Apple. But I think they’re taking the perfect path toward fixing it.