Production is ended. PLA have decided to end thus showing their opinion on these systems. I think it is a little premature to entirely abondon idea. On your point Type 89 gun technology is decades old if you read Sinodefence page you will see how long it took to develop and how 125mm smoothbore was chosen instead.
Whether it is a towed gun with APU making it mobile or put on a vehicle, it should atleast be capable as tank guns such as on Type 99. Plus fire all the same munitions.
The 120mm fires a one piece ammunition not comparable to the 125 on type-99. I don't see how they can fire the same ammunition.
AT gun is on the way out and quickly replaced by AT GM which is not lacking with PLA force structure. Look up the orbat and you'll see that AT GM is organic to many levels of units.