One Piece chapter 1115 revealed to fans more information about the mysterious character Joy Boy, the first pirate in history. This person also possesses Gear 5, but his form is a bit different. This shows that Luffy can still reach levels other than Gear 5.
Joy Boy's transformation, in addition to looking like Luffy's Gear 5, also has unique features: his hair is spiky and his surroundings, unlike the white clouds surrounding Luffy, Black predominates. Joy Boy also exudes more aggression, showing a level of strength that Luffy has yet to display.
Vegapunk even revealed that Joy Boy fought the World Government during the Void Century. Joy Boy is so strong that he and his allies can fight against the strongest person in the World Government.
Joy Boy's power, seemingly superior to Luffy's Gear 5, allows him to face the Five Elder Stars directly. The implication here is clear, if Joy Boy can do this then perhaps Luffy can do more than we have seen so far.
Although Luffy has proven that he is capable of defeating formidable opponents like Kaido, his fight against the Five Elder Stars shows that he still needs more strength.
The hypothesis of a new transformation is not only interesting but almost necessary. As the One Piece story approaches its climax, everything points to Luffy being able to unlock a never-before-seen form that rivals or even surpasses the power demonstrated by Joy Boy.
This development certainly sets the stage for revelations about the World Government's true power and secrets.
The final battle on Egghead Island could very well be the stage where Luffy finally reaches his full potential, fulfilling the prophecy of Joy Boy's return and possibly transforming into a force capable of overthrowing dump the world's oppressors.
Fans are certainly looking forward to what happens next, and with good reason: Oda seems to be grooming Luffy to not only become the Pirate King, but also a true liberator.