When could a dangerous situation arise here?

Your answer is correct because both situations you selected can lead to dangerous situations here.

First, if you continue driving at the same speed without being cautious, a dangerous situation could arise because the cyclist is about to leave the protected cycle path (indicated by the "Ende" sign). This means the cyclist might merge into your lane unexpectedly, especially since motor vehicles are about to share the road again.

Second, if the cyclist changes to your lane, this directly creates a conflict, because you need to adjust your speed or position to safely share the road. You must anticipate and be prepared to slow down or change your lane if needed to avoid a collision.

On the other hand, the cyclist stopping at the end of the cycle path is generally not dangerous in itself, as stopping on the sidewalk or cycle path doesn't immediately affect your driving lane.

In summary, the key rule here is that when a separated cycle path ends, cyclists merge into the main road, so as a driver you must reduce speed, be vigilant, and be prepared to share the lane safely to prevent any dangerous situations.