I've just read the technical deep dive article that the amazing writers at Eurogamer tackled on Project Scorpio, and noticed some very interesting news: AMD's next-gen Vega GPU architecture is making an appearance in Project Scorpio.
Project Scorpio rocks a mostly Polaris-based GPU, with technical features from the Polaris GPU architecture making up most of the soul of the new Xbox, but there are features like delta color compression that boosts bandwidth for 4K rendering and 4K textures. Microsoft took some of the improvements that AMD made in the Polaris architecture in Project Scorpio.
According to Andrew Goossen, Technical Fellow, Graphics told Eurogamer that performance optimizations from the next-gen Vega GPU architecture made it into the Scorpio Engine's design.