So, I haven't done this in a while and figured I should. First off, here are the deaths:
^I think all Atlanta survivors are (and should be) safe this season.
^I think that one of them is going to die toward the end of the season. It would also be a waste in my opinion if they killed off two of them at once.
^Only one will make it out of the season (hopefully they don't off them both...). I'm leaning more towards Sasha surviving at this point, though.
Karen-Dead. Either she will be the victim of the serial killer or will be killed later in the season in the assault.
Judith-Dead. I hope her death isn't too gruesome as in: No fucking walkers involved.
Woodburians-Dead. Do I need an explanation? They're redshirts.
Bob-Undecided. We don't know enough about him yet.
People who are obviously dead meat
Events in the first three episodes
I think the whole Big Spot sequence is the first thing we see in season 4. The first episode will mostly focus on showcasing how the prison group works. What their jobs are, who the new people are, etc. Then, all hell breaks loose when the walkers attack cellblock D and the herd almost knocks down the fence. The "threat from within" is a disease. Worrying that the disease is caused by the water, Carol goes outside to collect water from somewhere else/switch the irrigation system/something else to that effect. This would be where Carol escapes from the herd in the trailer. Tyreese has started a relationship with one of the Woodburians (maybe Karen?) who he discovers dead at the end of episode 1.
Episode 2 will probably take place entirely at the prison, allowing the viewers to catch their breath after the explosive first episode. Tyreese will be extremely thrown off by what happened in the previous episode, and will lash out at Rick and Daryl.
Episode 3 will be the one that focuses on Daryl, Tyreese, Michonne, and Bob on the supply run to either the Yates Plant or the College. On the way there, they hear the voice on the radio. On the way back, Tyreese's "gym scene" occurs. Michonne, Daryl, and Bob then get separated from Ty and run off into the forest. I think this may also be the episode in which Carl and Hershel are out in the forest, as well.
Episode 4 (which is NOT included in the trailer) will see Rick and Carol on a supply run.
The Governor's centric episodes are 6 and 7, if I recall.
I believe that the killer is the little girl speaking with Carol. I think that Carl develops a crush on her (similarily to comic-Sophia) while Carol adopts her (similarily to Andrea and Dale adopting the twins). Then, also like one of the twins, she murders two people at the end of episode 1. At some point this season, Carl kills her, believing that no one else would.
Remember, this is just a THEORY. Everything else under "events" is based off of evidence in the trailer.