We don't know anything for certain—this is just conjecture—but if our musings are what you consider to be spoilers, you may want to go read something else.
At the end of season three, Don Draper left Sterling Cooper to start Sterling Cooper Draper Pryce with, well, Roger Sterling, Bert Cooper, and Lane Pryce. They hired Peggy Olsen, Joan Holloway, Pete Campbell, and Harry Crane. We knew all those people would be back, but we figured everyone else would be left out in the cold. Well, then why is Ken Cosgrove in the cast photo for season four along with all the others listed above? We see in the final episode that Ken and Paul Kinsey were pissed that everyone was hired away from the firm but their incompetent asses, and we figured that was their death sentence. But there is Ken. Is he going to find a way to weasel his way back into the firm? Series creator Matthew Weiner hates when anything even potentially spoiler-worthy gets out into the public, how could AMC do this to him?
Also in the picture is Betty Draper, who divorced Don at the end of the season. We've long conjectured that this season would be the end of January Jones, who is often the worst thing about the show, but that doesn't appear to be happening. How is she going to figure into the action now that she's not a part of Don's life? And if he's not living at home, why has the diva actress Kiernan Shipka, who plays his lesbian daughter Sally, been bumped up to the opening credits?
So many questions, Mad Men! Hurry up and just start already, will you?