This could be true, but than again Orochimaru could have just been talking about the Sharingan's copy ability.
Orochimaru might have known about the existence of the Rinnegan and how to awaken it.... we would just need to know when he obtained Madara's body...
But, I believe he is thinking in terms of using the sharingan like Kakashi does, to copy jutsu...
He is not refering to the rinnengan lol...besides.... that affirmation is wrong.

ask me why and i'll tell you.
But u cant tell that he is reffering to rinnengan cause he aint... rinnengan cannot copy jutsu...
Come on guys.....
Of course you are lead to believe that Oro is talking about the Sharingan given the time in the manga etc....
but how can you deny that MASTERING EVERY TECHNIQUE IN THE WORLD IS NOT REFERRING TO RINNEGAN!! It is undeniable that this is a direct reference to the Rinnegan, no matter how you slice it. The sharingan's copy ability does not cover this. The only things that the sharingan can copy are things that do no require hand seals, things like taijutsu maneuvers, the rasengan and many other things, and techniques that are within the shinobi's repertoire of elements. Basically, Kakashi can only copy things like rasengan and things within his three elements, earth, lightning and water. I don't count anime, so Kakashi cannot actually copy fire or wind jutsu, simple fact.
However, Rinnegan gives the person the ability to use all elements. So a rinnegan user can theoretically
LEARN AND MASTER ALL TECHNIQUES IN THE WORLD, exactly what Oro stated. Of course, this only extends to the general elements so things like KG's are out of the question, but a rinnegan user can still master any single elemental technique that exists in the world, period.
I don't know how many more people are going to come in here and tell me Oro is referring strictly to the Sharingan because that is 100% impossible. If Kakashi could master any technique in the world, you'd think he'd at least have grand fireball jutsu within his repertoire right?
Everyone who is saying he's talking about the sharingan is retarded; in what way shape or from does a Sharingan allow you to use all jutsu?
This is the reason I hate reading threads here too many illogical clowns that will dispute anything because they didn't see it first or because it clashes with their theories *rant over*
Thank you, THANK YOU! Finally someone outright agrees with me that this must be a reference to the Rinngan. People might not like to accept it, but this is a direct reference to the Rinnegan, without a doubt. Not to mention, everyone knows that Oro believed a higher level of the jutsu was possible and even cultivated Hashirama's cells for that exact reason, come on people.