As we stepped up to the end of the greatest season yet, I wondered if Matthew Weiner might quit while he was ahead — and abruptly end the series on the highest of notes by shutting down the disintegrating Sterling Cooper Draper Price and sending his characters into the unknown. I needn’t have worried! With a marvelous set of twists that leaves us already drooling for the next round, MM is at once re-energized and up to its old dramatic tricks. Don’s sudden engagement is surely being argued over by fans, but it makes sense: his frayed emotional state leaves him open to impulse, and the relationship was presaged by Roger’s earlier 2nd marriage, as wisely pointed out by Joan in her bitch session with Peggy after Don reveals to the office what he and Megan are about to do. The final scene with Don and Betty (their first extended encounter since the break-up) was heartbreaking. And so pregnant with possibility. Is there the ghost of a chance they will reunite? Add that to Joan’s pregnancy and the company’s resurgence thanks to Topaz Pantyhose — and you have the potential for a just-as-magnificent Season 5. Bring it on! — Jeff Schultz