I believe he is a plot device. Lets face it. It is obvious sasuke is the final villain after madara is defeated so oro is needed to give him his last power up
If he was all talk sure, but he is responsible for the third Hokage death. experimenting with little kids is crazy. I'm still looking to see if Oro can perform Sage mode
I believe he's up to more. The guy just keeps coming back. Don't forget he said he still wants to take Sasuke's body. With 3 Hokages under his rule and the ability to unsummon Hashirama, he definitely pose a threat to the alliance after Madara's downfall. With such a weakened alliance after the war and everyone being exhausted, it's the perfect time for a snake like Orochimaru to strike who's been chillin the whole time. This could lead up to Naruto vs Sasuke final battle and what Naruto said about him and Sasuke would both die if they fought.
Anyways, this is just one of my scenarios. I definitely don't see him as just a plot device, I believe he's gonna be the game changer in the manga.
I think he is up to something. Imagine if his new goal would be to take over Obito's body. He's always had a thing for taking over an Uchiha body, and at this point I don't think Obito would be in any shape to resist.
Weaking sasuke right now would be the better option to use. But nah i dont really care. Since this fcking manga makes me want to quit right now bcoz of all those bs thaylt just happened..
There had been speculations of "Orochimaru can't be like this now; he is up to something". Something peaked out according to what he told Hiruzen in last chapter:
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"I don't want my experiments to cease away..." this is what he says; right?
A person does not want to give up on an experiment when it is not finished. If an experiment is finished; it is either reached it is potential; or a failure or a simple throw-out. It means the experiment is done for in any way and you would not continue; if you would that means it is not finished for you. The sentence suggests he has an ungoing experiment which he is not done with yet.
And look how he refers to Sasuke:
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Sasuke is the only "subject" for him that is yet to reach a certain potential; means not completed. He is possibly the "experiment" that he told about Hiruzen.
Orochimaru is still planning something regarding to his incomplete experiment; in this case, Sasuke.