For the people that still say this is a random event and not caused by the refugees entering Europe, these people are practicing something called "spiritual smugness". We are not saying all refugees are terrorists, but to deny that the two are not somehow connected, is ignorance in the face of apparent truth. Do not assume, but do not deny.
Acts of violence occur everyday but due to the attention of recent events, increased scrutiny and fear are natural. Focus any amount of attention on an issue or incident and people are going to look for trends. They do this as a way to try and understand why these incidences are happening. Additionally, they are looking for ways to prevent them from even happening in the first place.
The German trail attack will likely increase tensions between Europeans and refugees. Many Europeans already feel uneasy about their nations accepting so many Middle Eastern refugees. This latest terrorist attack will make many become nervous and fearful toward refugees. Therefore, it is likely that tensions over refugees will put political pressure on governments to curtail the number of refugees they accept.
Refugee tensions could definitely be increased after this attack. Any time violence is involved people generally turn to the easiest target to blame. Many time this is refugees because they are foreign and some people think they don't belong. Sadly, often a single event can place blame on a whole group of people.
Yes, sadly refuge tensions will increase because of the attack. It is likely that things will get worse. They are already high, and even though this attack was likely an isolated incident it will only make people fear outsiders even more. This is likely to cause more similar incidents and retaliation.