I think that if Matt makes it back in the game with one week of immunity that Rob will "make nice" with him and ask him to join with his old tribe in voting off Zapatera one by one. Rob could even say that once that is done then all bets are off and may the best man or woman win.
Rob is smart enough to know that once it gets to individual immunity that he will need the numbers on his side, so I expect to see him offer the olive branch to Matt in order to keep himself in the game longer. Andrea could (if she wants to) bring Matt up to speed about what has been going on within the tribe while he was away on RI. That way Matt would know who he should be wary of - other than Rob. Right now the other two girls are clearly not going to vote for Rob.