Adam won't do it if he wins. Shelly probably won't do it because she thinks she has a final three deal with them (even though she's guaranteed to get ZERO MONEY if she follows through with it). Rachel might if she recognizes that Jeff's her biggest threat to actually winning this game (or at least reaching the final two) and just says forget her alliance. Porsche and Kalia definitely would.
But then there's the Veto, and I'm sure BB realizes Jeff is in danger and they've made a Veto Competition suited to his abilities so he can get himself off the block.
--
"Why must we always choose between certain death and probable death?"
"I'm in an epic battle to the death, FIGURE IT OUT YOURSELF!"