According to MCU Exchange, Jeremy Renner’s Hawkeye is set to drop his mantle in ‘Avengers 4’, he will take up the popular comic persona of Ronin, in some iteration. Speculation began that Renner could make the switch when he was seen donning a new haircut on the set of the currently filming ‘Avengers 4’ in Japan.
Ronin is an alias of Clint Barton that he began donning after the Civil War comic event, becoming a member of the New Avengers. The name “Ronin” refers to a Japanese samurai without a master, a lone warrior of sorts.
The report also states that the events of ‘Infinity War’ leave Barton in a very dark place, leading to the mantle change. Also, the fact ‘Avengers 4’ takes place in some capacity in Japan may help lead to Barton choosing the name.
Source: MCU Exchange