I'm quite doubtful, that the PLA would adopt a 105mm, that would not at least be able to actually penetrate and destroy most if not all current active service 3th gen tanks.
As for future 4th gen (including heavier weights), the best tactic might be to just use some airbust or HE shot to disable aps, sensors etc. Afterwards a kill could be done with say atgm.
Regarding the debate over tank main gun caliber, I feel the necessity of "penetrating armor and stopping enemy rounds" is severely overestimated by military enthusiasts.
I believe this habit is indeed fostered by misconceptions stemming from video games, which portray the battlefield as much cleaner than reality (especially devoid of infantry or reconnaissance interference), and suggest that a tank is only "destroyed" by eliminating its entire crew or causing catastrophic explosion/fire. However, as we've observed in the Russia-Ukraine conflict, direct tank-to-tank engagements – especially unanticipated encounters without prior intelligence – have become virtually non-existent. Furthermore, in current combat, rendering an enemy tank combat ineffective is far easier than the stereotypical view: any damage or malfunction that prevents the tank from observing, aiming, or moving has a high probability of causing the crew to abandon the vehicle.
If we define "destroy" as temporarily preventing the enemy from actively employing the tank in combat, whether through abandonment or withdrawal, then the effective threat range of a 105mm gun with gun-launched missiles is almost indistinguishable from that of a 125mm gun AP shell,even better.
Setting the firepower standard at this level, combined with better intelligence enabling planned engagements, I see no problem with tanks reverting to 105mm. The only potential concern is whether the high-explosive (HE) or multi-purpose high-explosive anti-tank (HEAT) rounds fired by a 105mm gun can effectively clear enemies from buildings.
Building on this, my view is actually quite radical. I contend that tanks will not only revert to a combination of light and heavy tanks, but that future heavy tanks will likely be employed more like specialized equipment (e.g., mine-clearing vehicles). They would be attached to front-line units only in specific situations and in very limited numbers. Simultaneously, tanks equipped with smaller-caliber guns would serve not to withstand enemy fire, but merely as platforms to deliver a 105mm gun and its targeting system to the battlefield. Their armor would be merely to improve fault tolerance, not expected to absorb significant enemy firepower.
