In my opinion, it is too early if we judge that only the two top ranked teams at the moment will win the Bundesliga, because the league has only been running for 11 matches, meaning that not even half of the season has been underway, in my opinion there are teams below them that could still move up to the top rank to win the league. This season, including Borrussia dortmund, which is only ranked 5th, currently there is a chance, even though they have only got 21 points, they are 10 points behind Bayer Leverkusen, who have 31 points, the possibility is not too small for them because this is only the start of the season.
We are still having more than a half of season. Anything can happen during this time. People shall not forget that if the situation can change drastically. I think that people are judging based on the current performance. That makes sense since the team that leads the league is very consistent at this moment but people shall not forget the story about arsenal. The club was getting win streak for 33 weeks but it was losing against manchester city in the title race for EPL. The situation can change depending on the numerous factors.
Leverkusen is still the strongest team right now. This is why bayern needs also to surpass it as soon as possible. We will see which team that may be exhausted during mid till end of season. Dortmund needs to gain three points consistently as requirements to enter into the top 4 and title race.
FYI, the winter transfer season may give some changes to the club. Dortmund is always getting three points easily on UCL while it's always struggling in bundesliga.
Dortmund seems have its focus on the UCL instead of bundesliga.