I know this is no new theory, I'm just here to "revise, or add to" current theories. A lot of thinking has been put into this by myself. Doesn't it just make the most sense for darth plagueis the wise to of found a way to live on, and for sidious to continue training apprentices, while he observes his work from afar.
"Unfortunately, he taught his apprentice everything he knew. Then his apprentice killed him in his sleep. Ironic. He could save others from death, but not himself."
-Palpatine, to Anakin Skywalker
Did plagueis really teach sidious how to save himself from death? Did sidious make up the part about killing his former master? As to throw anakin off any trails that could lead him to his master.
When darth plagueis is first mentioned, in episode 3, a very distinct, low pitched humming is being heard in the background. This is the exact same noise played in TFA when we first are introduced to snoke.
"Snoke's just using you. For your power. Once he's through. He'll crush you". -Han solo
"Supreme Leader Snoke is WISE"- kylo ren
Maybe after he tried to create the ultimate dark side being in the galaxy, and it backfired (or did it?) resulting in anakin, the chosen one meant to bring balance to the force. Who was one of, if not the most powerful force user of all time. So maybe he was able to foreshadow coming events. Knowing that anakin would struggle with the dark and the light inside of him. That if he bought enough time, he could one day find someone with Skywalker blood (kylo ren) to carry on his work.
Personally I believe that is the reason kylo ren talks to his grandfather's helmet. Because snoke/plagueis has told him that "without me you would not exist" I created your bloodline through sheer will alone. Then I left sidious to continue my work. which would someday lead to the first order. Because he may of realized the faults in the galactic empire soon to come.
Did plagueis fake his own death to throw sidious off? Or did he and sidious come up with a plan to train new apprentices, so that he could stay alive as well.
The following is not considered canon (although I think that's soon to change.)
Darth plagueis was a Munn, who was also a business man In his own palpatine double life. Munns were known for being very intelligent. I find it, odd? that darth plagueis died the very same year anakin was released from slavery (32 bby(star wars date)). I think that plagueis and sidious had planned this all along. knowing that anakin was on his way to coruscant, they faked his death.
Actually plagueis "died" the night before palpatines election to become the new supreme chancellor. At this time anakin had already arrived in coruscant. Which means darth maul had already been sidious' apprentice for quite awhile, before plagueis died.
Not only that, but the exact same place where sidious told anakin of darth plagueis, is the same place where sidious and plagueis went on the night sidious "killed" him.
Also to those who will say snoke doesn't look like a munn, I bet they will make him look much better than the munn seen in episode 2.
I also believe that the darth plagueis novel will become canon based on its cover which shows something familiar. Only that's sidious kneeling before plagueis.
There's always that possibility that plagueis is a force ghost guiding kylo ren as snoke.. one thing is for sure, I know that snoke is a force user who Is probably very old. He is able to sense the location of Rey as being on the Millennium falcon, so he can either detect any force sensitive people, or those that he had a hand in creating. (Possibly rey, if she is lukes daughter) which leads me to think he is the wisest force user of all time.. darth plagueis.