If this season we can get two important titles from the Bundesliga and the Europa League then Xabi clearly deserves to be awarded as the best coach, plus if next season he wins another title then that is clear proof of Xabi greatness.
More big team will want him and he will also have much bigger salary cap.
Currently, I am sure he has made the list of the best coaches in Europe because of what he has achieved so far. This was why many too clubs were waiting for him to show interest in leaving Bayer Leverkusen so that they could immediately sign him. Having an unbeaten season will automatically qualify him for the award, however like you said winning the Bundesliga and the Europa makes him as the best candidate.
Of course, now Xabi has succeeded in becoming one of Europe best coaches, in fact I sure that he will get much bigger salary later when he leaves Leverkusen because of his performance which has been claimed as great coach.
Xabi two season showed big changes for Leverkusen and in this second season Xabi really had the upper hand in his performance in bringing Leverkusen to the top of the Bundesliga standings and becoming an unbeatable team.
He will truly be in the ranks of great and expensive coaches in the future even though when he was still playing, Xabi was not great player and had well-known name.
Xabi work this season has all started to look up not only in getting close to the Bundesliga title but for the DFB Cup which has made it to the final and also the struggle that has made Leverkusen strong enough candidate to win the Europa League.
If they succeed in winning these 3 competitions, it is clear that Xabi will be the only coach who can make Leverkusen have treble winner.