It would honestly surprise me if Kaiserslautern manages to beat them in the final.
They have a bit of a history together. When Lautern got relegated for the first time in 33 years in 1996 (together with us...) they played Leverkusen on the last day of the season and had to win against a very bad Leverkusen.
They lost and got relegated which resulted in the late Andy Brehme (WC Winner in 1990) crying on the pitch in the arms of Rudi Völler (WC Winner in 1990) who played for Leverkusen at that time.
Leverkusen playing Atalanta in the EL could cause them more trouble. Pretty interesting matchup as well because Leverkusen has a friendship with Offenbach while Atalanta has a friendship with Frankfurt.
Frankfurt and Offenbach are arch enemies with their grounds only 19 km driving distance apart so there surely will be Frankfurt/Offenbach fans present.