It is a bold thing to say that Dortmund won't be winning the Bundesliga title for sure in the coming a few years. But I can't deny the fact that Bayern Munich have been dominating this league for 11 seasons straight. Last season was the biggest opportunity for Dortmund to finish their series but they messed everything up in the final moment.
Now it is again up to Bayern Munich's performance level. As long as Tuchel has a good system working for them I will be expecting the continuation of this dominance from where it left. Dortmund can't deal with them while they are showing a high consistency. Dortmund can only benefit from a possible chance in case of Bayern Munich's being out-of-form.
Maybe Dortmund is saving money and they are planning for their next seasons to have a long-term plan. Because the way they make money by selling younger players is helping the team to save the potential for the next season and the players or coach they need. That's why I think maybe after a few years Dortmund can use this saved potential and finally win the Bundesliga title for years just like Bayern Munich.