Wolves may have been a serious threat to humans depending on the number of humans and the number of wolves. If humans were outnumbered by wolves then it stands to reason that humans would be at risk. Even today, with higher populations, many wolves still threaten humans. Not on a mass scale, but enough to warrant concern among communities to issue warning to keep pets and children safe.
I believe that wolves were indeed a serious threat to the survival of the human race. Before wolves were domesticated and became the forerunners of the dog breeds we know today, wolves competed with our ancestors for food, specifically meats. This competition would have made it difficult for early humans to have reliable sources of protein, a key element in their survival.
Sure, wolves have been a serious threat to humans in certain places and at specific points in history. There are many records of wolves attacking humans. However, this was normally due to humans moving into territories that wolves already occupied. I believe that humans are usually responsible for these attacks.
No, wolves have never posed a serious threat to humans. While wolves are indeed dangerous animals and are more than capable of killing a human, they have not posed more than an occasional threat to human beings. Wolves are not known to, nor have they been known to, systematically hunt humans in human settlements. Rather, wolves have been known to protect their territory from intrusion and to travel in relatively small packs compared to human settlements. Thus, wolves have posed a limited risk to small bands of humans and hunting parties, but not to humans in general. Further, the domestication of the wolf into the modern dog suggests that wolves and humans have coexisted peaceably enough for wolves to integrate into human society and become the faithful pets we know today.