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.
I am sure that the strong contenders for the Bundesliga trophy next season will not be Bayer Leverkusen with Bayern Munich, but Bayer Leverkusen with Dortmund, Leipzig or maybe another surprise team. Because I'm sure, Bayern Munich will still be in chaos because it seems like Bayern Munich chose the wrongcoach and because of that,I'm sure Bayern Munich will be out of contention for the Bundesliga title next season. With the chaos experienced by Bayern Munich,I also believe that the era of Bayern Munich in the Bandesliga is over and next, we might get several other teams who will win the Bundesliga trophy.