Microsoft Vice President has taken to Twitter to answer a question somebody had in regards to the Xbox One X. Ybarra confirmed that right now Xbox One X is certified for HDMI 2.0 and are aiming to be certified for 2.1 by November.
Xbox One X releases on November 7.
Certified for 2.0 now. Will certify for 2.1 when the spec is finalized (it isn't yet, hopefully by Nov).
— Mike Ybarra (@Qwik) August 29, 2017