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NOTE: THIS IS NOT THE THREAD WHERE THE MESSAGE BOARD POSTERS VOTE FOR THEIR 'OFFICIAL' PICK. THAT THREAD IS HERE
=========================================== Reward Challenge
We know the last place tribe will get "dissolved" into the other two tribes. We know that during the Immunity Challenge, Shii Ann is still shown in a Mogo Mogo green buff while Rob M and Tom still appear in Chapera red buffs -- implying that, assuming the members of the "dissolved" tribe get new buffs, the Mogo Mogo and Chapera tribes are not dissolved and therefore not the "losing tribe."
As to which of them actually wins the challenge, not only did RobM compete in a similar challenge during Survivor Marquesas, but he's also shown off his building skills in building the shelter -- and from the vidcaps, his raft looks pretty slick.
REWARD CHALLENGE WINNER: Chapera
Tribe Reshuffling
Assuming a Saboga loss, Ethan, Rupert, Jerri, and JennaL have to go somewhere. Based on the promo vidcaps, we know JennaL ends up on Chapera while Ethan ends up on Mogo Mogo. The wildcards are where Rupert and Jerri go. The most likely theory is that the tribe without Ethan would get Rupert and the tribe without JennaL would get Jerri, however the "two men battle for the crown of 'King Neptune' as fishing becomes a competition in and of itself" CBS press release mention raises the possibility that somehow Rupert and Rich end up on the same Mogo Mogo tribe, so that possibility has to be kept in mind as well.
Immunity Challenge
The immunity challenge is "balance beam log wrestling" -- very similar to challenges seen in several recent editions of the show. While this is not entirely a challenge of strength (balance is also important), a Mogo Mogo tribe featuring Ethan, Lex, Colby, and Richard would seem to have the advantage over Chapera's RobM, Tom, and Rupert -- and that assumes that Rupert even ends up on Chapera, an assumption that can not be guaranteed based on the existence of the "King Neptune" statement.
While Chapera's women might help even the odds, Alicia, Amber, Susan, and Jenna are, at first glance, not much more of an advantage versus Mogo's Kathy, Shii-Ann, and Jerri (assuming it was Jerri and not Rupert who was the second Saboga member picked for the Mogo tribe.)
Additionally the previews appear to show RobM making an illegal attack on Ethan and quite possibly disqualifying himself, a development that would put Chapera at an even bigger disadvantage.
Lastly, CBS' promos indicate that "a triumphant party is short-lived" -- something that might indicate the winner of the Reward challenge loses the Immunity Challenge.
In short, although several well-respected spoilers are projecting a Chapera win seemingly based primarily on the opinion that Richard, a Mogo Mogo member, will be the bootee, IMHO both the evidence and the majority of the logic point to a Mogo Mogo immunity win.
IMMUNITY CHALLENGE WINNER: Mogo Mogo
Bootee
As detailed above, a Mogo Mogo immunity win seems likely -- a move that would, barring another out-of-left-field game rules ejection or another sudden quitting player, make well-known marked man Richard Hatch seem to be safe for another three days (particularly since several of his tribemates like Lex have been clear that they were only keeping him around until they got access to their rice-filled lockbox -- and especially if Rupert, the game's other fisherman, were to somehow end up on Mogo Mogo.)
On Chapera, with the addition of two former Saboga members, Sue Hawk's previous status as the next most likely bootee might be clouded, but in the end, with the possibility of the "dissolved" tribe members being given one-time immunity (similar to last season's returning "ghost tribe"), as well as the general dislike that several Chapera tribe members have for Sue, Susan's booting would still have to be viewed as the most likely among the Chapera.
To sum it up:
RC Winner: CHAPERA
IC Winner: MOGO MOGO
Bootee: SUSAN ...and on the chance Chapera does somehow win immunity, RICHARD as the alternate bootee.