I think there is no person behind that mask. I think it is Specter controlling the body of the deceased Oliver Jonas Queen and feeding on Oliver rage. This theory depends if we learn what happened to his corpse.
Art is from Jack. Anyhow, I present to you a machine of battle, unyielding beast of destruction
There is no secret that J is a restless immortal billionaire, burdened by endless wealth yet starved for genuine excitement. For centuries he has drifted through existence, chasing diversions that never truly satisfy. Now, for the first time, he craves something more: an authentic thrill, a game that might break the monotony of eternity.
​
It is not beyond possibility that J, with his limitless resources and cunning, could ensure Bruce’s/Batman's survival by any means necessary. Whether through advanced preservation, forbidden sciences, or even the prospect of cloning in a distant cyberpunk future, J could keep the contest alive indefinitely. The game would never end, its stakes renewed across generations, its players reborn to continue the struggle.
​
In this vision, the figure known as Absolute Terry McGinnis may not simply be a successor but a living echo of Bruce himself. A clone shaped by circumstance, forged to carry the mantle forward. If Joker endures into that neon-lit future, then the cycle of rivalry and legacy could stretch far beyond the boundaries of mortality, binding them together in an endless dance with the devil in the pale moonlight.