Bayer Leverkusen going for another unbeatable season record isn't going to be an easy one but their chances of lifting the trophy back to back is still on the high side with Xabi Alonso still as their manager. Especially now that Bayern Munich who the very team have a tight competition with them has a new manager in place which I don't see the possibility of Bayer Munich up this season.
Xabi Alonso is prominent enough to handle the hurdles which will be coming his way next season. Remember he's the main reason behind the sudden peak form of Bayer Leverkusen, they're able to comprehend the situations at hand and hitting top target in each season. Bayer Leverkusen have relaxed their players and they're warming up for the big season ahead. This is not an easy one because the entailed actions involves other oppositions.
When teams do not evolve and improve over summer, expecting at least the same success is not reasonable because other teams keep improving. Like I believe Bayern improved more this summer than Leverkusen did, which means that we are going to see Bayern be better, and Leverkusen be worse than last season. This doesn't mean Bayern will win the title but it does give them the highest chance.
Xabi Alonso is a great manager there is no doubt about that but I also think that no matter how good a manager is and how great they did with that team we are going to see them start to be not great when the team doesn't improve every year. If Leverkusen wants more success, they should use the money they made to bring in more players that will help Xabi Alonso so that he would be able to get them good results again.