I'm guessing it's going to end up between 2060 Super and 2070 Super.
Phil Spencer said 2x Xbox One X. Many people (including myself initially) took this as being 12 Tflops.
But 12 Navi teraflops is actually more like 2.5x Xbox One X, which used Polaris. DF concluded that Navi is 1.28x Polaris so I'm using that for this calculation.
I'm guessing it ends up actually being like 9-10 Navi Tflops which has the performance of ~12 Polaris Tflops.
And 9-10 Navi Tflops is in the range of 2060 Super to 2070 Super.
GCN TFLOPS doesn't make any sense if you really think about it. Not only from marketing perspective, but actual numbers will not add up.
Remember Phil has said xbox SX will deliver 8x times xbox one power, so if you want to base your conclusions on GCN TFLOPS performance then you need around 10-11 Vega TFLOPS, and probably even less, because Vega was already way more efficient than customized first gen GCN found in standard xbox one.
So lest assume you would need 10TF Vega. Now in order to match 10TF Vega you need 8TF Navi and because xbox SX will use even better architecture than first gen RDNA (new features like VRS or HW RT are already confirmed) then we can assume even 7TF Navi 2 would already deliver 8x xbox one performance.
However the problem with 8-7TF navi is, it will not deliver 2x xbox x GPU performance no matter how you look at it. Xbox one X is using polaris architecture on steroids and just for comparison Xbox x with it's 6TF can deliver 2x times as many pixels as 4.2TF polaris found in PS4P. Obviously xbox x GPU architecture was already a clear step up from other polaris based GPU's. So even if you take into account Navi architecture you would need many TFLOPS in order to match 2x xbox x GPU performance, IMO you would need 10TF Navi at minimum in order to double xbox x performance.
So obviously Phil wasnt thinking about GCN performance, but pure TFLOPS number in general like he always did. 2x more 6 TFLOPS is 12TF and this particular number can perfectly explain what Phil has said in regards to xbox SX power. 1.4TF x8 is 11.2TF, so 12TF would be exactly over 8x times better compared to xbox one and also exactly 2x more compared to xbox x.
With windows central leak on top of that I'm certain MS is aiming at 12TF Navi. Of course thanks to RDNA2 architecture the performance gap between xbox x will be even bigger than numbers suggest but that's something casuals will never think about.