Much as it pains me to say it since I'm a big Caro fan, I have to be honest here and say "none of them." That doesn't mean that at one point someone from this group won't win one, but as of now there's no reason to believe that they will. I think that as we speak Serena, Maria and Vika have seperated themselves from the pack, not only on the ranking list but also as contenders for the majors. IF someone other than those three wins a(nother) slam title it's more likely to be Li Na or a Kvitova who gets her act back together. But the fun thing about sports is that you can never be 100% sure about anything, so....
Radwanska has an outside chance of winning one. She came within one set of doing just that at Wimbledon, so it's not impossible. She's kind of in the same position that Caroline was in a few years ago, but unfortunately for Aga she's up against a improved field of players. A lot of things would have to go her way, but if she keeps knocking on the door and makes it to the latter stages of slams on a consistent basis that door may one day open for her.
Kerber is a very good player and I can imagine her staying in the top 10 or close for several more years. But I also think that she has plateaued already and isn't going to improve much anymore.
Errani, I don't think so. She may make some deep runs (especially at the French), but her h2h against anyone in the top five is dreadful and to win a slam she will probably have to get past more than one of them. So I can't see it happen for her.
Wozniacki has, so I fear, already lost her window of opportunity. She missed the boat and started to struggle (for whatever reason) at almost exactly the same time as when the other big names of her age group (Kvitova, Azarenka and Radwanska) started to make their move. From the moment she fell overboard she's only seen that boat disappear ever further into the distance and it's going to take an allmighty swim to catch up again. Can she do it? The fan in me wants to say "yes", but the neutral observer side of me has to say, "probably not."
Jankovic. Are her recent great results just a last hurrah or is she really back? I'd say that it could be that she's back to some degree. I don't think she'll ever regain her former status, but getting back into the lower regions of the top 10 or close are not impossible and that would already be a triumph considering that up until recently we thought that her career was as good as over.
So no, I don't think that any of them will win a major, but if one of them does it will most likely be Aga. And I still have a tiny bit of hope (but it's not much more than that) that my Wozzy will prove me wrong.