“Avengers 4” starts production: "Beginning the End"

The official trailer for “Avengers: Infinity War” isn't even out yet, but the Russo Bros. are already on to the next installment.

The directors on Thursday posted a teaser image marking the beginning of filming for “Avengers 4”, and it's a glove showing off four digits. No word on who the glove belongs to, but the Russo's Facebook page has plenty of entertaining theories from fans, including commenters speculating it belongs to Captain America or time-traveling villain Kang the Conqueror.

Marvel has not revealed the title of “Avengers 4” yet because the title itself is a spoiler, and little is known of the company's plans following the movie. Only a 2019 “Spider-Man: Homecoming” sequel, due out two months after “Avengers 4”, and an undated “Guardians of the Galaxy Vol. 3” are on the docket officially. “Guardians” director James Gunn has said he and Marvel Studios chief Kevin Feige are tossing around ideas for the future of Marvel's cosmic movies.

Feige told Collider in April that 2018's “Infinity War” is the culmination of 10 years of storytelling, and that what comes next may be something different.

"Certainly as we get to 'Infinity War', there is a sense of a climax, if not a conclusion to, by the time we're at untitled 'Avengers 4', the 22 movies that will have encompassed the first three phases of the MCU [Marvel Cinematic Universe]," Feige said. "And what happens after that will be very different. I don't know if it's Phase 4, it might be a new thing.”

“Avengers: Infinity War” is set to open May 4, 2018, while “Avengers 4” will hit theaters May 3, 2019.