I don't think if leverkusen will lose 4 straight matches, considering their 9 up coming matches I think Frankfurt, dortmund, freiburg, stuttgart,this above mentioned club is considered been a threat to leverkusen. but I'm pretty sure that if leverkusen is going to lose I think it will only be 2of their matches, which is either to dortmund or freiburg,I don't consider the rest as threat to leverkusen instead of this teams to win leverkusen they will make it draw.
I no longer even consider all of these teams to be a threat to Leverkusen because Leverkusen's biggest threat this season is Bayern Munich and that team has also been defeated by Leverkusen this season. So I no longer consider all the teams you mentioned to be a serious threat to Leverkusen so it could be quite possible for Leverkusen to continue this unbeaten streak until the end of the season even though it is also possible for Leverkusen to get a draw in the remaining nine matches.