"it really all comes down to what Brooks wants to talk to them about on Sunday. "
Because of the inability from the authors to do something original, not a lot of choices:
the sudden visit of the girl that he turned down was probably to warn him of what was coming , probably some big orgy where he's tied on a chair and everyone have fun in front of him and zack and sophie being the stars of the show with impregnation before the crowd
or something more private , just brooks + the couple maybe his ex wife too where he invites felix to sit next to him on a chair (cuckhold ending he likes it starts faping etc)
maybe a special appearance of the black that joins in the orgy ending that rapes felix because honestly that guy has a gay face (zack & felix too).
expect nothing from felix's side, by the start of his thinking about acting and actually put thoughts into actions the guy will be celebrating christmas.
i wonder if i'm far from the truth but that's so generic i can't be 100% wrong