I had a few thoughts on this, YS. First, I'm sure it referred to the Starks. I think the title not only suggests vengeance, if not a resurgence, of the Starks. Yet, the word Time does not necessarily mean Victory. Furthermore, I think GRRM preferred the words Dream instead of Time and Spring instead of Wolves to reinforce the bittersweet ending he has in mind. Will the dream be realized? Will it still be in the future when the series ends?
I'm not an expert on North American mammals, but I've seen National Geographic, Animal Planet, and other media represent the lives of wolves. In short, summer is hard for the wolves, but winter is when they excel. The movement and health impeding effects of winter provide a bounty of food for the wolfpack. Wolves dominate the winter.
But as Eddard told Arya, wolves are strong only when they band together. I believe the pack will reunite. Sansa's political savvy, Arya's murderous skills, and Rickon's claim and fury will be the Starks' tools to carry out their agenda of taking down the Lannatheons, Lannisters, Greyjoys, Boltons, and Freys.
A Time for Wolves implies a Stark victory or at least justice for their slain. A Dream of Spring implies hope for all of Westeros and the world after the threat of The Other. I think the first title was too narrow for GRRM's epic and supernatural conclusion to the story. But I do think he wanted his readers to have hope in either title... so much tragedy has befallen the Starks that we must have some expectation that they'll survive and that the Lannisters will get theirs.
If Wert or Raven happen to notice this thread, I'm sure they'll give you all the answers.