Xabi is taking risk by staying in Leverkusen as they might not be able to repeat this success next season. With limited player resource, they will have big troubles by defending their Bundesliga title while discover Champions League. It will put Leverkusen under pressure of using their player resource very wisely to maintain good performances in Bundesliga but still don't affect their discovery about their own ability in Champions League.
They are both big tasks for Xabi Alonso and his players next season and I think Xabi decided to stay because he aims at a coach position in Real Madrid that is not available this summer. They will complete the contract with Carlo Ancelotti before finding a new coach in 2025 summer, not this coming summer next 3 months.
Whatever Alonso's decision certainly deserves respect from all parties because of course he has thought about all the possibilities that will happen to his career, but Alonso's stay at Leverkusen is certainly the right decision for him to continue to improve his coaching career, Alonso indeed cannot avoid the risks that may occur when he stays at Leverkusen and when if he fails in his second season with Leverkusen, So it is certain that in the future Munich and Liverpool will no longer make offers to him.
But I think Alonso's chances of success are quite open as long as he can maintain his current squad and at least if he is able to maintain Leverkusen's form in the Bundesliga next season, playing in the Champions League next season will certainly be a challenge for Alonso, because as a coach who is on the rise Alonso is required to be able to compete with the big European teams later in the Champions League, And this Is where it can be a form of proof from Alonso that indeed he deserves to be recognized as a great coach and not just luck to bring Leverkusen to be as great as this season.