The Latics host the League One Cherries in the third round on Saturday and could have Arsenal loanee Miyaichi in the squad alongside new signings Angelo Henriquez (on loan from Manchester United) and Honduran international Roger Espinoza (signed from Sporting Kansas City).
"Ryo has a chance for the FA Cup game," said Latics boss Roberto Martinez.
"He is 80% of his full fitness and is joining the main group this week.
"We hope he is going to be back very soon."
He added: "We're really excited about Angelo because he is a very young man with a huge potential.
"He is a goalscorer with clever movement inside the box and has had a very successful time with his former club Universidad.
"We hope to have a good partnership in terms of allowing Angelo to develop as a footballer and learn of the demands of the English game, because I feel he can bring us something different in the forward line.
"Saturday will provide him with the perfect opportunity to begin his experiences on the pitch in English football."