I've been thinking about the tribe switch and it seems to me that if the players are looking at the end game they'll be fighting over who gets to lose at immunity challenges.
Currently, old Nakum and Yaxha are even but with each having a majority on one of the tribes. So if new Nakum wins immunity that means that a member of old Nakum is going to be voted off, and vice versa. So every time the 4 members of old Nakum win immunity one of their former tribemates gets booted and they increase the chances of them being outnumbered after the merge.
And since, unless they never lose immunity, they will end up dividing themselves along old tribal lines because of the 4-3 split this means that old Yaxha will gladly rejoin the old tribemates at the merge and vote out those who previously had the majority over them.
Ugh! This could cause Stephenie to win simply because she keeps losing. The more she loses now the stronger her alliance gets.