At this point I wouldn't call it vaporware, its not that far along.
Most of the technology to do this is in place now. I won't try to argue that the current generation technology is actually cost-effective for drone delivery, but flight control, navigation, collision avoidance, etc., all exist in some form now. A hexacopter has some robustness (it can be designed to still fly with a single motor failure).
Most of the hurdles now are regulatory and economic. I don't know if those can be effectively surmounted, but if anyone can do it, I'm sure Amazon can.