Well, according to the Russo brothers themselves, he has already appeared in one of their adventures, namely Avengers: Endgame, but he was pretty hard to spot.
Fans have been longing for the avenging angel that is Frank Castle aka The Punisher to join The Avengers on the big screen in the Marvel Cinematic Universe.
No doubt he was pretty raging after having his tranquil stroll ruined by the sudden inclusion of a weaponized bench.