Kōhei Horikoshi's three official Twitter accounts for "My Hero Academia ("Boku no Hero Academia")posted today November 23, 2020 a teaser puzzle visual for the what can we assumed to be a third film adaptation of the series. The visual which was separated into 3 parts were posted on each of the anime's website: official site, official movie site, and manga page on the Shounen JUMP site.
The said video teaser show the three heroine of the series which is Deku, Bakugou and Todoroki with a teaser quotes "He will meet 'the three musketeers'." The picture above is a Teaser Visual which might explain the three parted video teaser for the assumption of the 3rd Movie..
The 3-part teaser visual can be found here:
1st: https://heroaca.com/
Twitter: https://twitter.com/heroaca_anime/status/1330708017361219584
2nd: https://heroaca-movie.com/
Twitter: https://twitter.com/heroaca_movie/status/1330707747797487626
3rd: https://www.shonenjump.com/j/rensai/myhero.html
Twitter: https://twitter.com/myheroacademia/status/1330707679870742528