According to this guy, Lloyd is going to get possessed by this ghost named Morro in the season after the Tournament of Elements (season 5)
But could Lloyd actually turn evil without being possessed? Think about it, Misako and Lord/Sensei Garmadon had Lloyd while Garmadon still had evil/the Great Devourer's venom running through his veins from when he got bit by the Great Devourer . Because of genetics, Lloyd could possibly have the venom of the Great Devourer inside of him. Meaning that Garmadon could have passed down the Great Devourer's venom into Lloyd when he was born.
In the final episode of the Tournament of Elements season, before Sensei Garmadon decides to enter the cursed realm in order to get the Anacondrai generals to curse Chen and his army of false Anacondrai, Lloyd goes on like a 10 second rampage against Chen's army in anger. This can hint that Lloyd will lose himself when he loses a loved one. Perhaps by the end of the 5th season, another one of Lloyd's loved ones die and he loses himself again, unleashing the evil inside of him and basically becoming Lord Garmadon II, who goes on a longer than a 10 second rampage, or something.
Oh well, that's just a theory.