There is a paper thin report about it, but it's been reported over at The Hollywood Reporter that Todd Phillips will return to pen the script for a sequel to his 2019 Oscar-nominated film Joker.
The first film, which notably was tonally and narratively inspired by early Scorsese films like Taxi Driver and The King of Comedy, saw the titular character re-vamped as a failed comedian named Arthur Fleck in Gotham City in the late-1970's/early-1980's. After shooting three upperclass who nearly beat him to death, Arthur begins a downward spiral into madness, ultimately becoming a nihilist who finds society as heartless and thus unknowingly ignites an anarchist movement in the city. Joaquin Phoenix played the part and went on to win the Oscar for Best Actor for his role.
It's uncertain at this time whether Phoenix will return in the role or if Scott Silver, who co-wrote the first film with Phillips, will return in any capacity for the sequel. It's not even confirmed at this time whether Phillips will return to direct or simply remain as a screenwriter, though reports indicate he strongly intends to. For now, it goes as no surprise a sequel is being worked on. Despite claims the first film would remain a standalone entry, it surprisingly went on to make $1 billion at the box office and was nominated for 9 other Oscars at the Academy Awards including Best Picture. Stay tuned!