Copy-paste of some choice paragraphs regarding Plagueis.
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First off though, this talk that Disney is trying to distance themselves from the PT is far too black and white. Yes, TFA was very OT-heavy in it's inspiration, though still there were some PT references, including the idea of balancing the Force in the very first scene. But I think this was their way of giving the film series a sort of "soft reboot" so that afterwards people can trust them if/when they do reference the PT. But Disney will be ignoring the PT completely? Nope. Look at Rebels, that show is littered with prequel and TCW references, not to mention characters. The novels are tying into both the OT and PT. We're getting a comic about Obi-Wan and Anakin. The Kanan comic depicted Order 66. The Princess Leia comic involved Naboo and Queen Amidala. All of that is under Disney and more specifically the Story Group. Now, probably the most surprising, The Art of The Force Awakens shows definitively that they were experimenting with the concept of Hayden Christensen returning as Anakin's force ghost (which was rumored before, and is still rumored to occur in VIII). They even got Ewan McGregor to record lines for Obi-Wan. I'm sure they want to avoid aspects of the PT that weren't well received, but the mention of Darth Plagueis the Wise is hardly considered one of those aspects.
Disney would be complete idiots to never reference the PT again. An entire generation grew up on the PT and another grew up on TCW. Disney is about making money. They aren't going to ignore those demographics.
Back to Snoke=Plagueis. There are too many ambiguous things that LucasFilm has gone out of their way on regarding Snoke. Snoke is "humanoid" not any locked down species. Most other new alien has a species name already. Why doesn't Snoke? Pablo doesn't mind decisively saying that "it wasn't Zuvio killed in the force vision, it was a human guy" yet dances around the Plagueis topic with cryptic statements. At this point if it wasn't Plagueis, then why hasn't he or Disney said as much outright? What would they lose by saying that? It would do nothing to the mystery of the character, if anything it would redirect speculation toward other ideas in a positive way. The music is too close of a match to be coincidence. Way too close. John Williams knows what he's doing. The line "The Supreme Leader is wise." The movie should have put the nail in the coffin if it wasn't true, but those things alone have fueled the theory even more. Never mind all the other points that seem to fit - his being around for a long time but outside the Galactic Civil War, his damaged state, descriptions from the crew of him being like a corpse which was reflected on-screen.
If it's true and they do intend to reveal him later on, the writers will do it right. They aren't going to have him say "I am Darth Plagueis!" without some indication first of the significance of that, and where he's been referenced before. Even then, a big-chinned purple guy smiled at the camera after The Avengers and most of the world completely missed the significance of who that was. Yet now people get it. Plagueis is much less of a stretch than that, he's already been established in one of the Episodes, and was a key motivation for Anakin to become Darth Vader. Personally, I think it would be a lot more work from a storytelling perspective to explain that he was an Admiral that we've never seen or heard of and what his significance is, or that he's an extra-galactic force of pure evil and he has this long history with Luke that we never saw.