I would say that it is possible for Ja/Ca to U-Turn, but only after they have completed the other side of the Detour, since a team is not allowed to use a U-Turn before completing the Detour, and they technically have not completed their Detour.
Yes, I would agree with you on that point. Sorry, I forgot to convey that in my previous post.
The question is, does anyone else U-Turn, and if so, who is it?
I wouldn't think so.
I'm assuming at this point that K/V and Ja/Ca are well towards the back of the pack (K/V because of how far behind they are at this point, and Ja/Ca because they are with them.) Although Zev & Justin are not yet accounted for in the previews, bar one close up that gives us no frame of reference with the other teams.
that the K/V & Ja/Ca are the bottom two for the whole leg, and Zev & Justin will catch a leveller to put them with all the others. Assuming this is correct, other teams might not be U-Turning simply because of how far behind K/V & Ja/Ca are, so they figure that their target will not get eliminated.
EDIT: But then of course we have the cap of Vyxsin with Luke and what looks like Kisha or Jen in the background, so there goes my whole "Kent and Vyxsin are so far behind so nobody bothers U-Turning" theory