The animated TV show Star Wars Rebels recently introduced time travel which showed Ezra going back in time to save Ahsoka from being killed by Darth Vader.
Although the main reason Ezra wanted to go through the portal was to save Kanan, he was warned that he would be creating a paradox meaning Kanan had to die to save Ezra’s life.
Regarding Palpatine’s death, a Reddit user has come up with a theory saying,“He’s [Palpatine] able to open a portal into the World Between Worlds, but he can only see and hear through it. He’s standing over blue force fire which he sends through the portal after Ezra and Ahsoka.”
“The fire grabs Ezra by the leg, and the Emperor is then able to briefly reach his arm through the portal before Ahsoka frees Ezra. Ahsoka goes back to her timeline, Ezra goes back to his, and the Emperor is unable to get in. Ezra seals the only known gateway into this realm, and then the gateway is destroyed.”
“Being able to have access to the World Between Worlds would make it a more powerful weapon than the Death Star. It not only allows him to travel backward and forward through time and space, it can allow him to see who his enemies are, where they are, and what they’re planning.”
“However, it’s a one-way trip if you go completely through a portal, the gateway (which is now destroyed) is the only portal that allows you to get in. As of right now, there doesn’t seem to be a way for anyone to ever get back to the World Between Worlds. However, the Emperor was powerful enough to create a link to Ezra while he was in the realm and nearly got in by using his blue force fire.
“I’m sure that in the years between this episode and Return of the Jedi, the Emperor spent time trying to find a way in.”
They added: “As for why I don’t think the Emperor died in Return of the Jedi, it’s because his death involved disappearing after an explosion of blue force fire.”
“The large blue explosion engulfs the entire shaft he was thrown down. Oddly, it doesn’t cause any damage to the surrounding area.”
“I think this is the same blue energy that allowed the Emperor to enter the World Between Worlds. This is where he disappeared to at the end of Return of the Jedi.”
“To avoid a paradox, he chose a portal to the future: after the death of Snoke and Luke. Maybe even after the death of Kylo Ren.”
Some believe that Palpatine returns as Snoke, but this can be ruled out based on what we know.
Star Wars Episode 9 releases December 2019.