There have always been theories about a book before its release date. Some speculate about a character or the title or both. Here are what my thoughts were before a respective Survivors book came out. I would also form theories when I was reading the book. These are all the theories I can remember (if not more) at the moment. :P
The Empty City
When I first visited the Survivors website, I made a theory that Lucky and his friends would encounter the Fierce Dogs in the city and his friends would all be captured by them.
The crow following Lucky would be waiting for his death.
A Hidden Enemy
I thought that "Zeke" would be a good name for the dog on the front cover, before his name was revealed to be Alpha.
Thought that "Deer" would be a good name for the tan dog, who is later revealed to be Sweet.
I'm not sure when I thought this, but I thought that Bruno would be the villain and the one who displeased the Earth-Dog.
Lucky would return to the Wild Pack to warn them, just when the Fierce Dogs appear.
The Broken Path
Thought that the dog behind Lucky would be either Old Hunter or Fiery.
"Rabbit" would turn out to be Alpha's real name.
Three days after I read the book, I thought that Old Hunter was actually Terror, which was disproven a year later.
The Endless Lake
Storm would be trying to convince Blade to not attack her Pack.
I thought that Terror might return in this book, but I know he's dead now. :P
Storm of Dogs
Thought the prologue would take place during Lucky's puphood and Lucky would see his mother's death.
Lucky or Sweet would fall into a chasm and fall to their death.
Lucky would die in the battle.
Storm would die a heroic death and join Lightning in the sky as partners.
Every single dog would die from the battle.
Mulch would be revealed to be the Fear-Dog, a theory disproven on page 268 of this book.
Whine and Dart would abandon the Pack to go to who-knows-where.
The Wild Pack and Fierce Pack would join together to face "Terror's Pack."
Alpha would betray the Fierce Dogs.
We would find out which dog displeased the Earth-Dog. Personally, I thought that it would be Alpha, Whine, Old Hunter, Terror, or even Lucky.
Terror would be at the heart of the Storm of Dogs and try to take down the Wild Pack and the Fierce Dogs with his old Pack. Also disproven.
When I first saw the Pack List, I thought that Twitch might be the real enemy. People might think that wasn't true, but you never know what changes a dog.