Cas is most probably going to speak up for and protect Jack and , oh boy, Dean's going to be super pissed, having to go through all of the drama once again ;/ On the side not, I know that the fandom is disturbed by how cavalier Sam was about Jody but Dean leaving Sam all alone with Jack - a ticking bomb - wasn't ?
They literally just needed a way to get them split up, it’s pretty much that simple. Sometimes it’s not a deeply analytical reason it’s just “get to point B in the plot”.
However Jody and Dean would have died if not for Patience’s vision. Patience was the hero even though Dean did kill the wraith he was on super not good form, his running and fight sequences made him look old, tired and like he didn’t particularly care about winning/surviving. It was so well done. LBR in 13x06 he’s going to be super badass and people will be like yay Dean’s got it back! He’s no longer OOC! We will be like yeah no shit I wonder why ;)
Dean letting Sam make his own decisions and not telling him what to do, Sam standing up for himself (I so want more weird Sam fashion choices to make this clearer please, it’s the fun side of it instead of just him arguing with Dean!) is another example of letting go of his parenting and the toxic codependency, so they made it fit into the character arcs too.