Jay is there for sure, barring a Jimmy/Kelly/Jade situation. I genuinely have no idea on the other three. Having Jay as the only male finalist in a series where they've now said a couple of times they want a male winner would probably make the agenda too obvious, but I don't see Jeremy being the first comedy contestant since Julian to make the final, and Peter's involvement with the show seems an after-thought : since week 1 he's got the same sort of scores and the same sort of mostly positive but not blowaway comments from the judges. That could all change but if he finds himself in the dance-off with most of the other frontrunners, on current form he'd probably lose.
Of the women I think Carol, Jamelia and Kirsty can safely be written off, but that still leaves 5. Helen is the judges favourite but I don't know about her ability to connect to a wider audience and she's by no means bulletproof in a dance off against Jay or Kellie. Kellie has a lot of momentum at the moment, and Kevin "Never In A Dance Off" Clifton, but seems to increasingly be Marmite, has the Eastenders Fatigue problem waiting and also almost certainly isn't on the tour, for those who want to factor that in. Anita is good and seems to be growing in popularity but it's hard to tell yet whether the Gleb Factor and how hard he's being pushed is a help or a hinderance. Katie is at her lowest ebb, but has a good draw coming up and a ready-made and likable storyline in "is this Anton's year?" (although I suspect with the advent of free online multivoting this is going to be less impactful than it would have been in earlier series). Georgia is a mystery - she could be completely passed over by the public or she could have exactly the sort of "juvenile soapie sweetheart" personality this show's voters have gone for in the past.
Again, outside of Jay, it's very hard to tell, but I'm currently guessing at Jay, Helen, Anita and CAN Management registering multiple e-mail addresses a week to power Peter to the end.