A few months ago, I published an article detailing how Tanaka was sending strong hints that he would not return to Xeno for awhile.
We got that confirmation in a new blog post in which he roughly says:
”“I’m doing an illustration for this [KOS-MOS] figurine. This is probably my final job for Xeno artwork.”
While still not a definitive “I will never work on any Xeno games again” answer, I think it’s fair to say that Tanaka Kunihiko will not be returning in and having a part in future Xeno games.