So, Kabuto said that he couldn't retrieve Lord Jiraiya because his body sank deep under the ocean. But in my opinion, his body will float (if he is dead and his body survives the hungry fishes) and he will be brought back as an EDO-TENSEI either by ORO or KABUTO, if they track him.
But here's an other probability: Let's suppose he was able to perform Kuchiyose no jutsu when he was drowning and with the help of toads he was brought back to Mt. Myo and was kept and treated secretly.
But still there is one thing that weakens my theory and that is: "why would Lord Fukasaku keep it secret from Naruto or Tsunade?" and here is the antidote to this: "'coz Jiraiya wanted so."
There are many things else than that and i think I'll post a separate thread for this.
Well, it's all up to M. Kishi. Let's see how he wants to run the things.

[I hope we see Lord Jiraiya again alive and healthy

]