First of all, there are no more rich clubs like Bayern Munich in the Bundesliga. Secondly, neither team probably wants to compete with Bayern Munich for the title. The Dortmund team is quite strong. Had Dortmund not sold their best players every season they could have built a squad capable of competing for the title with Bayern Munich. But they don't. And this is why we see only Bayern Munich's dominance in the Bundesliga every season. Next season we will see the dominance of Munich.
Dortmund does not seem too disappointed to fail this season. Their orientation is not always champions, Dortmund are smart in doing football business. They have always done that, selling some star players to Bayern Munich. Maybe strong dominance still belongs to Bayern Munich but looking at Dortmund they have a chance to win the Bundesliga. In fact, it is still quite difficult to guess. Quality players do not guarantee a club the league title.