Pure speculation:

They all witness the duel and after Sarita is defeated, Matt joins the others and they all merge.

This leaves 12:
Rob (i)
Natalie
Andrea
Phillip
Ashley
Grant
Ralph (i)
Mike
Steve
David
Julie
Matt

They will have an IC and 1 gets immunity and possibly immunity for Matt as the returnee.

Matt will join Rob, David most likely will join Rob, we know that Grant, Andrea, Natalie, and Ashley will all stay clinging to Rob. They will oust Phillip (who is getting dangerous at this point in the game) and one of the original Zap's in a double boot.

At the end of the episode they then have 10 players on the new merge tribe.

I think that Phillip then goes on his own immunity run at RI, his editing seems to indicate that he will go farther than just merge, he may even be the one that re-enters at F5.

I'm not sure who came first hosting games, you or Tribe, but you are both nefarious! - CTGirl