Man, if this is true that Sony has Navi, while MS gets stuck with Vega, I'd imagine that we're going to be seeing an exact repeat of this gen, including the power difference between the OG consoles in GPU power, with the same Zen CPUs. Not looking good for Xbox.
My guess would be that only Navi 10 is exclusive to PS5, if it's even exclusive at all. MS will still have access to Navi 14 in 2020 I would assume. We know that MS doesn't just design one hardware prototype for a new console, they actually design multiple prototypes then finalize the prototype that best suits their price/performance needs in the year they plan to launch in.
I could see something like this for MS right now prototype wise:
Goal- 2019 release, in case Sony releases PS5 in 2019
CPU- 4-6 Zen Mobile cores, 8-12 threads (Zen mobile cores in use instead of Zen desktop cores to reduce CPU power usage as much as possible, to leave more room for GPU power usage)
GPU- Custom Vega 20 based GPU, which is cut down and underclocked to reduce power usage some, roughly 10-11 tflops, so a 70% increase in GPU power over XB1 X or more.
RAM- 12 GB GDDR6
Hard drive- Probably 2 TB standard hard drive paired with 64GB of SSD cache to speed up load times
Price- Fluid. MS will be waiting to see how much PS5 is before they announce a price, then will undercut that price by $50-100, even if they have to sell at a loss to do it. Since this theoretical 2019 Xbox Scarlett would most likely be weaker than PS5 using Navi 10, MS will know they need to have the cheaper console if they want to be competitive.
Goal- 2020 release, if Sony plans to release PS5 in 2020
CPU- 6-8 Zen mobile cores, 12-16 threads
GPU- Custom Navi 14 based GPU, cut down or underclocked to reduce power usage some, roughly 12-14 tflops.
RAM- 16 GB GDDR6
Hard Drive- Probably 2 TB standard hard drive paired with 128GB of SSD cache to speed up load times
Price- Semi-fluid, but most likely $500