Follow-up to 2009's Sherlock Holmes and 2011's Sherlock Holmes: A Game of Shadows, the threequel has yet to officially confirm the return of Robert Downey Jr. as the iconic sleuth and co-star Jude Law, who plays his mystery-solving partner Dr. John Watson.
The third installment in the series was said to still be a "top priority" for Warner Bros. despite Downey's production company, Team Downey, exiting the studio after six years in late 2016.
Downey and Law head the series inspired by Sir Arthur Conan Doyle's famed detective mysteries, launched nearly a decade ago under director Guy Ritchie, who is now in post on Disney's live-action Aladdin re-imagining.
That first Holmes entry scooped $524 million worldwide, outdone by its sequel with $545 million for a combined $1.069 billion.
Series producer Lionel Wigram remarked in 2015 the stars were both "very, very" interested in reprising their roles, saying "we would all love to do one if we could come up with something that really was going to knock it out of the park and was going to be the best of the three."
The planned Sherlock Holmes 3 tapped Iron Man 3 scribe Drew Pearce in 2011 before drafting James Coyne (Puncture Wounds) in 2016.
Most recently, Warner Bros. and Village Roadshow put together a writers room to develop a script, recruiting Nicole Perlman (Guardians of the Galaxy), Gary Whitta (Rogue One), Justin Malen (Baywatch), Geneva Dworet-Robertson (Tomb Raider) and Kiern Fitzgerald (Snowden).
Downey is expected to return to the franchise as he made clear his intentions to make a third Sherlock Holmes in March, telling Entertainment Weekly he and wife-slash-producing partner Susan Downey were "looking at another Sherlock Holmes" in addition to the star's in-development Perry Mason for HBO.
The actor still hopes to headline a live-action Pinocchio, where he would play Geppetto, the puppet boy's father.
Downey can now be seen in Avengers: Infinity War, which continues to break records after earning the biggest worldwide opening in movie history and becoming the fastest film to reach the $1 billion milestone.5comments
The superstar next heads The Voyage of Doctor Dolittle, where he plays the titular physician capable of talking to animals. His Spider-Man co-star Tom Holland will lend his voice to 'Jip,' a dog, in a cast that includes Octavia Spencer, Ralph Fiennes, Emma Thompson, Marion Cotillard, Kumail Nanjiani, Rami Malek, Craig Robinson, Frances de la Tour, Selena Gomez, and John Cena.
Sherlock Holmes 3 opens December 25, 2020.