Jason begins by telling the audience that every relationship reaches the "So..." moment, where someone in the relationship will want to take the relationship to a more serious place.
At that point, Jason knows the relationship is over, as he is not ready to start dating.
Jason has just been dumped, but he didn't even realize they were going out.
Meanwhile, Mikey's wife has just asked him for a divorce, and perpetually single Daniel is still single.
The boys are going to have to juggle their single life with their romantic entanglements and it's going to get awkward.