User blog comment:Omega natsu2/Chapter 373: Let Live Or Let Die, Predictions./@comment-24551285-20140224070236/@comment-7418318-20140224104233

As far as I remember, Karin meet Kabuto after he started to mess with his body. While Orochimaru's essence might have been drawn out of him, that still leaves all the other DNA or whatever that Kabuto incorporated into his own body.

And on top of that there's the sage mode, so it's still possible that it might be Kabuto.

Either way I seriously doubt it'd be Jiraiya, since Karin said something about the chakra of the mystery person feeling bad. And being revived by Nagato would't have done Jiraiya any good with him being at the bottom of a lake or ocean so deep that his corpse couldn't be retrieved by Kabuto. He'd just "re-drown" right after coming back to life. And if the frogs had saved his dead body, they'd surely have turned it over to the Leafe village so he could be buried at home.