Q3 2016 release date is too early to put out anything. Takes time to test and make sure everything syncs. Even if Apple got early processors to test, it would still not be out.
When Apple updates the Mac Pro, these posts will be forgotten and everyone got their blood pressure up for nothing.
It's amazing that people think innovation is easy and can be done quickly, even in a year or two year time frame. Phil and crew probably spent a few years on the Mac Pro. That is why I think he said, "innovation my a@@".
He was proud of the Mac Pro. It was all over his face at the keynote. Open it up and take a look at the design. Awesome and took a lot of work to get all of the custom everything to talk together. Not defending Apple, but understand a bit about technology innovation and design in my younger adventurous days.
Yes, it had or has some bugs and issues, but this is first generation design and a complete custom job. My opinion of course, but designing it completely from scratch takes time to make sure everything works out the door, which probably they needed more time to make sure the dual graphics and metal works together and other things...but they needed to get it out so people would stop complaining that they are taking too long between updates. Everyone demands yearly updates or it is considered "old" technology.
I think they are taking longer to make sure all of the new complexities work and may have had issues with consistency. Thunderbolt 3, 4K to 5k and advance pci busses etc. came to maturity or is still since the last Mac Pro came out. They might have switched out or stopped midway in design to start over or implement other technologies and therefore takes more engineering time etc. just my opinion of course.
http://wccftech.com/intel-kaby-lake-q3-2016-cannonlake-2017/