http://gematsu.com/2016/05/rumor-smalle ... x-one-2017
The slim X1 will apparently have a 2TB hard drive right out of the box. Microsoft, I loathe you as a company, but even I have to give you kudos for including an actually decent-sized hard drive. Also for making a slim model in the first place, because let's face it, X1 NEEDS a slim version.
The more powerful X1, apparently codenamed Scorpio, will have a more powerful GPU and Oculus Rift support. Microsoft is reported to be pursuing a partnership with the makers of the Rift. In addition, the Scorpio will be capable of supporting 4K resolution.
Some more interesting tidbits:
Microsoft is reportedly also moving toward an iterative approach for their consoles. Instead of one hardware revision every five years or so, the company is planning a more incremental model, with more frequent hardware releases and games that are both forwards and backwards compatible across both Windows 10 and different Xbox models.
The current Xbox One is believed to operate a peak target of 1.32 teraflops, compared to the 1.84 teraflop performance of PlayStation 4. The 2017-due Xbox One is said to have a performance target of 6 teraflops, while the rumored PlayStation 4 upgrade, code-named “Neo,” is said to run at 4.14 teraflops.
All of that said, “universal compatibility” is said to be a core principle for the new system, which is currently being designed to support all Xbox One software.
If all of this is true, I think it's safe to say that the 8th gen has just turned into the Cold Console War. We cannot afford a teraflop gap!