I think they're petrified it will be a Travis, Aisha and Skye final three. These three get along like a house on fire. That doesn't make for very exciting tv. Aisha and Travis are psychotically jealous of each other, but Aisha isn't jealous of Skye so there wouldn't be any fire works. Travis and Aisha rarely disagree. They will just pash and sunbake. Hardly must see tv. Plus they share fans, so they split the voting 3 ways.
On the other hand if you have Skye, her nemesis Ryan and Lawson, the good magician gone bad as a final 3, people will be voting like mad to prevent Lawson from winning, even if the don't especially like the other two. Plus people will be very divided between Skye and Ryan, especially if they spend the week fighting, creating way more of a voting frenzy. It doesn't necessarily have to be these three, but i suspect they want people who don't get along so having Priya and David in the mix is another option as they don't get along. But Aisha, Travis and Skye might just not be very exciting.