As Sam and Dean get in the Metallicar, Missouri calls out to them, "Don't you boys be strangers." And then adds, "See you around." Oh, you betcha, Loretta Devine! The Metallicar chugs off, accompanied, sadly, by strings rather than Scorpions.
Cut to Missouri entering her house. She walks through a doorway, puts her hand on her hip, and says to someone off-screen, "That boy. He has such powerful abilities. Why he couldn't sense his own father, I have no idea." The camera swings around to reveal John Winchester sitting on the couch with his head in his hands. He says, "Mary's spirit. Do you really think she saved the boys?" John stares sadly at his wedding ring until Missouri breaks in, "John Winchester, I could just slap you. Why won't you go talk to your children?" He replies that he wants to, that she can't imagine how much he wants to see them, but that he can't: "Not yet. Not until I know the truth." Which, if I'm counting correctly, will be about eight episodes from now. Don't hold your breath.