What Xabi Alonso and his team have been doing in the Bundesliga is very extraordinary and unimaginable. He has beaten multiple records in the Bundesliga by being unbeaten for so long. But I would agree with @Iranus. Bayern Munich are still the favorites to win this title. There will be a time when Bayer Leverkusen will drop points Bayern Munich will get some points to get ahead of them. But I think the match that will have the most impact on this championship title race is the match between Bayern Munich and Bayer Leverkusen. Whoever wins this match will get a good advantage, even if it is 1 point. I mean 1 point is a lot considering how the current race is going. Bayern Munich knows how to gain back their lead I believe.
Leverkusen became the strongest team thanks to the polish made by Xabi Alonso because before Xabi became Leverkusen coach, Leverkusen often sat in the middle of the standings, even last season they were in the relegation zone but Xabi Alonso saved them. Xabi Alonso became a big hero in Leverkusen progress in the Bundesliga so nothing can stop Leverkusen if Xabi Alonso is still with them. Even though some of them still think that Leverkusen is not ready to become champions, the proof is that they are able to sit at the top of the standings for a long time and that shows their seriousness in breaking Bayern Munich dominance.
The Bundesliga is dominated by Bayern Munich as the strongest candidate to win the trophy but we want to look at other teams and Leverkusen should be able to do it this season. To win trophy, of course Xabi Alonso has to recruit several new players in this transfer market because they have to compete until the end of the season if you look at their points tally which is very close to Bayern Munich who are in second place.