When announcing its new desktop computer at WWDC, Apple would only reveal that the device will launch 'this fall'. However, clicking the Mac Pro 'Notify me' button on its homepage now clearly states that the desktop is 'Coming September'.
Notably, the product page for the Mac Pro and the notify me link on that page still says 'Coming This Fall'. Perhaps Apple had originally targeted September for release but decided to play it safe by specifying a broader timeframe.
You can learn more about the 2019 Mac Pro and Pro Display XDR here. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.