Sources told the San Jose Mercury News that prosecutors will likely announce the decision soon.
McDonald was arrested Aug. 31 on suspicion of domestic violence while celebrating his 30th birthday at his home with teammates and friends. He has continued to practice and play throughout -- he has 12 tackles this season -- as coach Jim Harbaugh, general manager Trent Baalke and CEO Jed York have said they would allow "due process" to play out.
Police said the alleged victim had "visible injuries." McDonald lives at the home with his fiancee.
Two court arraignment hearings have been delayed.
The Associated Press contributed to this report.