Keith will kick off Scott and Holly for the following reasons:
1. Strategically, Keith has always known that Scott is one of the strongest players. When Charla and Tara wanted to kick off Alex, Keith said that the smart move was to eliminate Scott. He said you have to take out the top dog. Keith might have no idea that a jury vote will happen, but he has to view that as a possibility. His best strategy would be to keep a couple that is arguably even less popular than he and Tara. Keith has never been anything but strategic.
2. Keith is still resentful about how he was treated by the originals. During his excursion with Holly, she said she felt bad about standing by while DKCT were attacked, and Keith responded in essence, "Like Hell you were upset."
3. Keith and Tara are extremely loyal to Charla. They would never kick off Dave if there was any chance that Charla would also go.
4. Despite Dave's recent behavior, he has had the power over and over again in this game. And Dave has done the foursome's dirty work, sending home Beau (twice), Tom, Kristin, etc. Keith will remember the fact that Dave never sent him packing when he had the power.
5. Dave said in his Boston Herald interview that he keeps in touch with all contestants apart from one person. That person is obviously Toni. If Keith and Tara backstabbed him, there is no way that he would so quickly forgive their betrayal.
6. Keith left himself an out. When he spoke to Scott, he said if Scott gave him the power, he might still have to vote out Scott and Holly. Therefore, if he decides to save Dave and Charla, he hasn't lied to anyone.
Of course, the above analysis could fall to pieces if Keith has a sudden embolism and loses all capacity for rational thought. In other words, if he turned into Dave.