Zack Snyder is currently filming the Justice League movie in London, and now Jared Leto is there.
It's unknown if Jared Leto is in London for a Joker appearance in Justice League, but the actor did take to his social networks to announce he is in the city (via reddit).
Jared Leto stars as the Joker in Suicide Squad, which hits August 5th. It's thought Jared Leto's appearance isn't just a one-and-done, but it's speculated Leto has signed a multi-picture deal to appear as the Clown Prince of Crime.
It's possible Jared Leto could cameo in the Justice League movie as the Joker, which would be followed up by a large role in the solo Ben Affleck Batman movie (some fans think Red Hood).
"Justice League" has a November 17, 2017 release directed by Zack Snyder starring Ben Affleck as Batman, Henry Cavill as Superman, Gal Gadot as Wonder Woman, Jason Momoa as Aquaman, Ezra Miller as The Flash, Ray Fisher as Cyborg, J.K. Simmons as Commissioner Gordon and Willem Dafoe in an unknown role.