I think realistically the likely candidates are those who have already been in the bottom two (Penny, John, Letitia and Kenny) as well as Kate.
Based on what they're doing
Penny - could possibly struggle a little with her control during the salsa. May however look fabulous. She's a really hard one to call until we've seen some training footage. She does seem to lack public support though if you see her position on our poll and remember she ended up in the dance off from a very strong position on the leader board two weeks ago.
Kate - on past form her salsa will be dreadful and she won't cope out of Anton's hold. I hope, for her sake, I am proved wrong as she does a decent job. If she is okay again it may lose her the sympathy vote and it could be curtains for her.
John - John is better at the Latin but somehow he doesn't seem to inspire people to vote for him.
Letitia - I'm slightly concerned about her VW. She is large up top (in the bets possible way

) yet has those lovely long, skinny legs and being slightly top heavy may play havock with her ability to spin and stay steady, purely because her centre of gravity is a little higher. Her popularity does seem to be increasing though.
Kenny - Kenny seems to have stayed in the last two weeks on a mixture of sheer entertainment value (that samba was damn funny) and showing a bit of thigh (well it works for the girls - good on him!

). I think he may possibly struggle to win over the public with the more sedate and less showy VW.
Overall I think Penny is in danger if she isn't high enough up the leader board and Kenny is probably the most likely person to join her in the bottom two. Having said that, on the night things can change very drastically so I'll probably revise this once I've seen them dance!