For the last 9-10 seasons we have seen only Bayern Munich dominate the Bundesliga. The team performed brilliantly from the beginning to the end of the season and won the title every season. However, the scenario in the Bundesliga last season was different. After Bayern Munich lost their best striker, Lewandowski, their performance became somewhat erratic, while their performance deteriorated further due to a change in coach. This allowed Dortmund and Union Berlin to occupy the top spot in the table. Bayern Munich will not make the same mistake next season. They will take all necessary steps to stabilize and strengthen the team and the club is ready to spend a lot of money. This is why it is expected that next season we will see only Bayern Munich dominate.
Since Bayern Munich did experience some irregularities last season it would be premature to write off Dortmund chances going forward. Football is a sport that can be unexpected and teams results may vary. Dortmund has continually demonstrated their tenacity and potential to be a title contender. Furthermore even though Bayern Munich administration is spending money to bolster their team success is not guaranteed right away. Football is a team sport and many things go into making it successful. Other teams will work to catch up because the Bundesliga is known for its fierce competition. It is a fascinating period for German football and how the upcoming seasons play out remains to be seen.
Indeed, there will always be tough competition in the Bundesliga between Borussia dortmund and Bayern Munich, but hey, we have to know the reasons why Dortmund have always failed in several seasons to shift Munich's position, it's all done because of business.
I won't go too far into what I mean, of course we know and about the future of a Bundesliga club like Bayern Munich, we don't know what will happen, but until a few years later it seems difficult for another club to replace Bayern Munich.