in the battle between orochimaru and the 3rd orochimaru try'd to summon three things 1 being the 1st hokage 1 being the 2nd hokage but the 3rd (no points for guessing who it will be) was blocked by the 3rd. At some point naruto will fight orochimaru who will use the 3rd summon (or rather 4th!!. at some point in the fight he will reveal he is narutos father. Revelation, father and son do battle. (possible title of episode there) .If im right im right if im wrong it was a pretty good guess
i also think during this battle kyubi will be released by the 4th