Is it? At the 2013 WWDC, Apple revealed the cMP. That was in June. Units headed out to shipment by very late December. If the new Mac Pro is due in 2019, it makes sense to preview something now to get people riled up and eager to order. If they wait until September/October, it'll cast a shadow on their other impending releases. People are more likely to order more if they have a clear idea and aren't offered too many products all at once. And if they wait until the next WWDC and release in December 2019, then there will be a 6 year delay between the cMP and the new Mac Pro. At which point, most Mac Pro users may get tired of waiting and move towards Windows systems.