I will not put my money on Bayern Leverkusen beating Bayern Munic when they meet next because the present Bayern Munic is doing much better than Leverkusen. Besides, it will be a big slap on the face of Bayern Munic to be beaten home and away by Bayern Leverkusen, hence I don't see this happening this season again. If I were Xabi Alonso, I will aim for a draw with Bayern Munic and then concentrate in winning other teams and avoiding drawing smaller teams as much as possible. Nevertheless, it will be an interesting match that will likely decide how the league will end because if the gap between those two top teams widens, it makes winning the league easier for Bayern Munic.
Just because it will be a "big slap" in Bayern's face, that doesn't mean it cannot happen. Also, that Bayern's home loss to Leverkusen was a DFB Pokal game, not the league game, so it's possible that Kompany did not prioritise it the same as league games or the Champions League. Their last league clash was a 1-1 draw (in Munich).
So considering their head-to-head results, Leverkusen should be the favourite to win. But of course, current form is much more important than past stats, and there will be quite a few games to go before those two meet on 15th Feb, so we'll have a better picture closer to that date.
ps. it's "Bayer" Leverkusen, not "Bayern".