Complications can be caused by sympathy voting for the bottom dancers, with the effect that those a little way above the bottom can end up in the drop zone, perhaps John or even Mark.
Wonder if Gary (and Karen) will get many sympathy votes.
Also it's the judges who actually get the final say, in principle based on the dance-off, but in reality based on their expectaions.
If Don should be in the bottom 2, they might well decide that he has future potential, a bit like John Barnes (who kept getting saved), and save him.