The QJZ89 HMG is due for a replacement.
To be replaced with what though. It is highly doubtful that the PLA will go back to any HMG design that is heavier than the 89, and as you said there is only so much weight saving you can do before it negatively effects other areas of the gun's performance.
I think this whole research is more to prove a point than to turn out anything useable, which is weight is not something that can be shave off as one likes it without any compromises.
In fact this last decade alone has been a major experimenting period for the PLA in terms of ammo sizes. They try to eliminate the intermediate 7.62 round and push the 12.7mm into it's place, but it seems that they just can't overcome the performance gap.