If B decides not to show for court, the aggravated assault charge will be dropped against A, that's if it wasn't charged as a domestic violence. If it were charged as an DV, then the State would pick the charges up.
A would still have to face three very serious criminal charges in NJ.
1. N.J.S.A. 2C:39-5 Unlawful Possession of a Weapon
2. N.J.S.A. 2C:39-4 Possession of a Weapon for an Unlawful Purpose
3. N.J.S.A. 2C:39-3 Prohibited Weapons and Devices
And being that the State has witnesses, the weapon and two statements (from both A and B), it's safe to say that A will never have a job in law enforcement.
The long wait is because the case was sent to the county and they are backed up with other cases. Once the case is in the hands of the prosecutor, they will decide what charges and if there is enough evidence for conviction. Once they decide, the case is sent to a grand jury to decide if it should be dealt with in Superior Court or sent back to Municipal Court for trial.
If A is indicted, a warrant will issue and A can and likely will be arrested. Start saving for bail.