A Shang-Chi movie is reportedly in development, but Marvel actually first announced it was working on a film based on the Asian super hero back in 2005.
Prior to Iron Man (the first official Marvel Cinematic Universe movie) being released in 2008, Marvel Studios announced it had raised $525 million to make its own movies based off Marvel properties. At the time, a slew of possible Marvel movies were announced: Avengers, Captain America, Black Panther, Ant-Man, Dr. Strange, Hawkeye, Nick Fury, Cloak & Dagger, Power Pack and, of course, Shang-Chi.
Source: IGN.com Marvel First Announced a Shang-Chi Movie 13 Years Ago