The outcome of Bayern Munich and Bayern Leverkusen will determine if Dortmund will remain in the first position. Their is high probability Bayern Munich will win the game. It is interesting to watch Dortmund and Bayern Munich fighting to be at the top , right now it is still unpredicted to know who will win the league this season.
I think that today it is very much possible, that Bayern Munich will not win their match against Bayer Leverkusen. In the last few games Bayern Leverkusen was in a very good shape both in the Bundesliga and also in the Europa League. Leverkusen has a very talented squad with a lot of young players that have a huge potential. If they are feeling well and confident they can be dangerous to every other club. In addition to that Leverkusen is playing at home, so this is another small advantage for them.
That being said, Bayern Munich is stil the strongest team of the Bundesliga by far and if everything goes relatively normal, then Bayern should win today too, but you never know.