Once you have been arrested and charged with a crime how long does the state have to present the case to the grand jury and get an indictment? The charge is ID Fraud
While it is true that the state has four years to formally charge a person once they are aware of the crime, you will likely be indicted within a very short window if this is a Fulton Couty case. The practice in Fulton County is to indict everything and investigate later as opposed to some other counties that take a long time to investigate before indicting.
You should get an attorney involved immediately to see if there is any way to prevent the formal charges from moving forward. You better move fast, though.