Well-respected Japanese newspaper Tokyo Sports reported on their website that Chris Jericho is still under contract to WWE despite his upcoming match against Kenny Omega at Wrestle Kingdom 12.
The actual web page is in Japanese, and though the sentence structure can be difficult to read through even when Google translated, the article is a fascinating read.
Tokyo Sports wrote that, "Although Jericho is not full-time, he still has a deal with WWE, so of course Vince (President McMahon) is also giving permission for this entry, although the real intention is not certain”.
Of particular interest there is the claim that Vince McMahon gave Jericho express permission to pursue the match with Omega at New Japan Pro Wrestling's biggest annual show. Wrestle Kingdom is akin to Japan's WrestleMania, so it'd be a break from the norm for McMahon to show interest in promoting anything that big outside WWE.
During his own media appearances discussing the match, Omega has made sure to talk up New Japan and disparage WWE's system. It appears the entire package is being presented as serious Japanese wrestling vs. WWE 'Sports Entertainment'.