“Mad Men” wrapped up season three last night with a furious-paced hour of decisions and changes.

The principals of Sterling Cooper have decamped to start a new agency. The good news is that Joan will be with them, and that Jared Harris’s character of Layne Price has become a prtner in the new agency. Peggy, Pete, and Harry Crane are all along for the ride. The change also means that Sal, who was fired after his gay incident with a client, will likely return and kickstart Sterling Cooper Draper Pryce’s involvement in commercials, TV and film. Sal could become the Joel Schumacher of “Mad Men.”

(I am also still hoping for a crossover with another fictitious ad agency of the era: McMahon Tate. Maybe Don can run into Darren and Larry at lunch one day.)

At home, Don and Betty are kaput. It’s ironic, but Betty is the philanderer. Don’s infidelities remain hidden from her. A new Don dawns in the new year, 1964, when the show resumes. Jon Hamm’s Don will now be freed from his marriage and his past. That will be exciting — a smart move by Matthew Weiner. I will miss Conrad Hilton. Actor Chelcie Ross easily deserves an Emmy for series guest star.

Still, John Slattery’s Roger Sterling remains my favorite character. No one delivers a line like Slattery. He almost swats them away, like flies. His cadence sets the rhythm of the room.

What was interesting in all this was the effect of the Kennedy assassination on all the characters. Subtly, the shock of it has changed their lives. Everyone is re-evaluating. Betty, who is horrid, nevertheless see her chance at strength. What will happen to her is anyone’s guess. It looks like she isn’t taking money from Don, and depending on new love Harry Francis. That already looks like a recipe for disaster. But no one will miss Betty, not Don, the kids, or the audience.

The best news is the return of Joan, played by Christina Hendricks. We didn’t see enough of her in these last thirteen episodes. She should be a bright shining star in the next go-round — and certainly matched with Slattery, Hendricks will make her way to the lead.

What comes next: the Beatles, the civil rights movement, LBJ, women’s lib, bra burning, the anti-war movement, and, oh yes, as Don said to Peggy, “Negroes.” Maybe we’ll see a black employee at the new agency. Wouldn’t that be something?