I don't doubt Xabi Alonso because what they got this season is the result of his hard work since last season, not just luck, so it is possible that this can continue or even get better.
The heavy pressure next season will definitely be from Bayern Munich who will grow even stronger to compete for the title and of course that will make the Bundesliga competition even more competitive.
I guess it will be cant getting better as they have played the whole season of the german league and its hard to top that.
Leverkusen have to proof themself now in the Champions League , but i think that they will be doing that.
Bayern Munich for sure have already the pressure and with the change of the Coach and few players leave it will be not easy.
There's so much uncertainty in the mind of football fans across the globe regarding the future of Bayer Leverkusen in the coming seasons after their great achievements of the just concluded season. The club achieved so many surprising results that many people never thought they would get at the beginning of the season and now that they went on to defile the odds, the question now is id they can retain impressive performance beyond the just concluded season. Xabi Alonso isn't a magician and everything he achieved this season never came with luck but because of how he mastered the act of coaching so I strongly believe that he'll still continue to record good results with the club if he continues to remain at the club.
It's always easier to win the league title than to successfully defend it so I know it'll be difficult for Bayer Leverkusen to retain the league title come next season since Bayern Munich now have a new manager but i strongly believe that they stand a good chance of winning the German Bundesliga title again come next season.