Power Wise :-
First off, there is no way Orochimaru can stand up aganist Naruto and Sasuke. Oro getting negged in one to two panels would not be amusing to anybody. Naruto and Sasuke at this point (15 years since the war) would have already surpassed Hagoromo because thier powers given by Hagoromo would have matured. So, if Orochimaru intends to stand up aganist them, he either needs an equivalent power, i.e; Madara's Rinnegan or somehow gets to be connected to Kaguya (Where theories speculate Oro being Kaguya's Husband). With Madara's Rinnegan; Oro can fight easily aganist Naruto and Sasuke.
PloT Wise :-
All of Orochimaru's research on Kaguya's Lineage and the Rinnegan points to the God Tree's Fruit. By eating it Oro can fulfill his dream. but, in order to get the God Tree's Fruit; the Juubi's power is essential. The container, Gedo Mazou got sealed away. There is no way Sasuke and Naruto would ever ally with Oro, so he will have to bypass the seal. This is where Madara's Rinnegan comes to play.