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.
Well maybe the big teams aren't a threat but football sometimes can be really funny and maybe you can be surprised that it might even be one of the little teams that even give them problems in their quest to keep a clear stand and achieve something that very hard to do which is keeping an unbeaten record through out the whole league. Bayern Leverkusen have really shocked many this season and they have defiled all odds and is heading to win the bundesLiga but you can never be too certain because one bad spell can spoil everything.
It is understandable that Leverkusen consistency can be stopped by a small team that is not taken into account at all, this is a fact that we have often seen so far. That why Xabi is still unable to talk about their chances of winning the trophy, because he understands that everything can change in the blink of an eye. I think it's not a problem to just assume that Leverkusen can win the trophy this season, where Xabi fleet is already one step closer to achieving success.
Leverkusen don't have to maintain their unbeaten record throughout the season, what's more important is winning trophies, but if they manage to do that then that would be even more wonderful. Personally, I'm not too worried if Leverkusen loses points, because as we can see they still have a safe point difference from Bayern.
Leverkusen toughest challenge is in the Europa League, it seems they have a little difficulty winning easily there, very different from their matches in the Bundesliga or DFB Pokal. Among the three competitions they are currently playing, the DFB Pokal trophy seems to be in their hands, it's just a matter of time.