I don't think this condition will last until the end because indeed for Union Berlin itself, even though they are currently good, I still don't really believe in them.
Union Berlin gives me Newcastle vibes in the premier league. A team that started very well but don't look like they can keep up with the momentum needed to finish first but just at the top four. Union Berlin already lost the top position this season and are still very unreliable with their inconsistent performance, so I am in doubts. Union Berlin play against Bayern next, and that is an important game in the title race, both teams will be looking to win to stay level with Dortmund should they win their game too or top the table should Dortmund loose or draw their game against Hoffenheim. Bayern are not having a great season, so there is still the possibility that they loose to Union Berlin, the underdogs for that encounter.