I agree with you that the decision to leave or stay is a double-edged sword, on the other hand this is an opportunity to change fate and career to a high level, but it all depends on Xabi decision between leaving this zone or staying. and the possible difficulty of finding other opportunities. In my opinion, Xabi should stay longer at Leverkusen to prove that there he really has a big influence on the team's performance, not just luck. Xabi does have the qualities of a great coach. 1 more season with Leverkusen is enough and he can accept the offer.
I also want him to stay in Leverkusen for another year because everyone sees his success this year as a coincidence. If he stays in the team next year and shows similar performance, he will show everyone that this is not a coincidence, but talent. Xabi was a great player and now he is a great coach. Leverkusen owes him a lot.
Good work from him in this season which helps the Bayer Leverkusen to have title with record breaker wins we are going to have good chance as well for him to stay here for the another season but as we also have few big offers from the few top clubs he can also leave even this all is not easy, but all is possible.
Two offers are on his table, but mostly fans are looking for the official statement which is coming after the end of this season while they are having historic work and their chances for the double is also high because they are having good chance into UEFA Europa cup which is also now enter into top eight teams which are competing for the title and right now we have Liverpool and Bayer Leverkusen as the favourite teams.