I don't think so. Leverkusen sold two of their best players. Even so, the bonding between the players in the squad is not weak. Leverkusen still has a stable squad.
So qualifying for the Champions League should not be difficult for Leverkusen. Teams like Dortmund and Leipzig are not consistent in their performances. We see these teams performing irregularly almost every season.
Its not only about the key and best players that left Leverkusen , the most will be the change of the coach.
For now i would say that it will be very hard the coming season for Leverkusen.
Dortmund and fingers crossed here hopefully will be better in the season.
Leipzig is behind the performance they can do.