While such a thing is certainly likely down the line, IGN recently asked Jared Leto what the Joker would make of the other major hero with DC’s universe.
The Joker and Superman would be interesting to see onscreen because Superman’s so stoic and morally centred.
As it turns out, Jared Leto already has an idea what he’d like to do.
The characters of Joker and Superman are such opposites, that watching them go up against each other would be something special to see.