They won't even come close to relegation because the team on 16th position has 18 points less compared to Dortmund, they won't even reach BVB's 35 points this season, most likely not even close. So nobody should even mention Dortmund and relegation in 1 sentence, cause it's basically impossible to happen.
If they get their shit together they can still reach Europe, but that's a tough task of course. After some winnable games there will be a barrage of top teams waiting for them.
Dortmund is actually far from falling into the relegation zone because of the point gap between them and their teams currently in that zone. They may have played poorly in the past and a lot of them already making it look like they can’t stand a chance in the fight for an Europe spot next season. I still think they will want to try as I see their journey in the champions league is already coming to an end. They can at least get a spot in the European competition next season if they try more but I don’t see them in the champions league next season when they get eliminated from the competition now.