Zardnaar
Legend
In canon Palpatine spent a lot of time trying to wipe the Jedi out and he died in RoS. However idk if the Jedi or sith can ever be wiped out forever even if you kill every single one. For the following reasons.
1. Force Ghosts/Sith spirits.
Well they exist and can guide or advise any wanna be apprentices. Momin in the new canon is an example of a Sith spirit along with Bane in the clone wars.
2. Holocron.
If any order is ever truly wiped out holocrons survive. Containing knowledge one can still learn the ways of the force using them.
3. Clones.
Palpatine can perhaps move his spirit around clone bodies. He could in legends maybe in canon as I'm not 100% sure on the exact method he used to come back. Or did a clone die in RoS and the real Palpatine can still exist. Or he can transfer into a new clone body who knows.
4. Hidden/secret apprentice. There's a 30 year gap between RotJ and TFA. Palpatine could have an unknown apprentice in that time. Additionally there's a lot of unexplained time for Darth Maul before his death in Rebels. Other Jedi may have survived the purge.
Legends Material Perhaps Applicable to Canon.
5. Carbonite/stasis.
Legends did go there canon has not. But we don't know how long one can be frozen in Carbonite. Ancient sith Lord on ice can be done or other form of stasis.
6. Pre Bane/Other Sith Order.
It's possible more Sith could exist either in a remote part of space or extra galactic eg in the dwarf galaxy Kamini is located in or even another galaxy.
Do that's just a few ideas several from canon and a couple that were used in legends but logically are possible in universe.
1. Force Ghosts/Sith spirits.
Well they exist and can guide or advise any wanna be apprentices. Momin in the new canon is an example of a Sith spirit along with Bane in the clone wars.
2. Holocron.
If any order is ever truly wiped out holocrons survive. Containing knowledge one can still learn the ways of the force using them.
3. Clones.
Palpatine can perhaps move his spirit around clone bodies. He could in legends maybe in canon as I'm not 100% sure on the exact method he used to come back. Or did a clone die in RoS and the real Palpatine can still exist. Or he can transfer into a new clone body who knows.
4. Hidden/secret apprentice. There's a 30 year gap between RotJ and TFA. Palpatine could have an unknown apprentice in that time. Additionally there's a lot of unexplained time for Darth Maul before his death in Rebels. Other Jedi may have survived the purge.
Legends Material Perhaps Applicable to Canon.
5. Carbonite/stasis.
Legends did go there canon has not. But we don't know how long one can be frozen in Carbonite. Ancient sith Lord on ice can be done or other form of stasis.
6. Pre Bane/Other Sith Order.
It's possible more Sith could exist either in a remote part of space or extra galactic eg in the dwarf galaxy Kamini is located in or even another galaxy.
Do that's just a few ideas several from canon and a couple that were used in legends but logically are possible in universe.