Liverpool is also looking for him which is also challenging, but he needs to take his time and then decide whether he wants to join the toughest league like Premier League or going to stay here in this current league with now having good chance for Champions League and things surely could be not easy, but surely it's going to be one of the best time for starting new career.
usually when a coach achieves success in one of the popular teams, the coach will usually stay for a few more seasons to try to bring Leverkusen to a higher level and win the UCL title, breaking new history and this is often done by other reliable coaches.
from here I have the idea that Leverkusen management will definitely keep Xabi to stay with Leverkusen for the next season or maybe until his contract is finished.
but if after this season ends and Xabi decides to leave Leverkusen, it would be a very bad decision and I'm not sure if he can find success in a team from another league.