A modular expandable Mac Pro has no future in today's Apple, but...maybe they'll surprise us down the road.
Unfortunately, Apple has literally become what they so much derided in their underdog years--a company that is concerned only with power and money (IBM, Microsoft, etc.). When was the last time something was truly revolutionary like iPhone? That was 2007. They follow the majority consumer instead of leading them as in years past.
Then, when they switched to an in-house SOC, I actually had my hopes up that they would innovate considering abundant financial resources and now tighter control. BUT now, it is more than obvious that goal is not to innovate, but to only boost their income and tighten their stranglehold on others' innovation. I'll continue to follow the Apple journey, but the path (or lack thereof) doesn't look good.