This is what he has to think about because after all, when he is in a new team, even if it is Madrid where he has a big attachment when he was a player, it doesn't necessarily mean that he can succeed there because there are some other factors that are sometimes difficult to explain by the coach where he was very good at the previous club but actually deteriorated at the new club.
So with this decision must be taken carefully so that Xabi's ambition to be at a big club does not backfire on himself. he is now very good for Leverkusen and indeed the increase in Leverkusen, which was originally in the relegation zone last season until it returned at this time to become one of the troublesome clubs, is proof that he is playing very well and the chemistry between him and the players is well maintained here. But it does not mean that he also has to be stuck in one place if he is sure enough of what he is doing to move clubs and can maintain his performance it can also be an option but if he is not sure about that then staying at Leverkusen is a good choice.
Personally I think Xabi should not be coaching a big club now. I have no doubt that he is an excellent coach. But he is still not experienced enough. I think Xabi still doesn't know properly how to handle a lot of star players. Leverkusen is a mediocre team. And there are not many star players in this team. So it is possible that Xabi can manage the team as he wants. But managing star players is a bit difficult. As we have seen coach Pochettino was unsuccessful with PSG despite being quite experienced. PSG's squad had many star players, and coach Pochettino failed to strengthen the understanding among these players. Xabi should make a decision to coach a big team after gaining more experience.
It could be an alternative but ultimately it comes back to Xabi himself because the decisions he makes are important too. Indeed, being at Leverkusen can be a good thing because in the end he can learn a lot before making some breakthroughs by moving to a bigger club but on the other hand, if indeed his ambition is very big to be at a big club and is ready to accept the risks in the next season by risking his career then indeed being at Leverkusen will also not make him happy so it is necessary to understand that what Xabi now wants to do. Club offers are likely to come in for him and Leverkusen also give full discretion whether to stay or leave so Xabi's decision to take action is important.