It is believed by some scientist to have caused the Toba Catastrophe Theory, resulting in a 'bottleneck' in early human populations.
The region is most definitely still very active with continuing seismic and volcanic activity.
What would be the precursors to a repeat of a Lake Toba super-eruption?
I think this question is not specific to Toba, but rather to volcanic eruptions in general. there is a lot of literature about that. You may want to start with the wikipedia article on that topic.