Well it seems the PLA may as well wait for ETC and Magnetized Plasma gun tech to reach MBT sizes for its 4th gen tank. Rather than simply slapping a 130mm or higher bore gun onto some better suited possibly unmanned turret with emphasis on new modular armour and APS. Well all the rest but with better firepower using ETC and MPA guns. If mach 6 is possible with even current APFSDS materials and density, it'll be nearly three times the kinetic energy compared to the best penetrators in PLA now. That's possibly gonna let it penetrate a M1A2 riding behind another M1A2 lol... I'm jk but yeah mach 6 penetrators will basically go through whatever you put in front of it. Give it high density depleted uranium and longer length and watch it slice through multiple heavy MBTs like a 155mm firing from <1km would.
IMO penetrators with 1000+ pen doesn't really help much at the moment... Unless your opponent is Leo II lol. Slapping a 140 onto 4th gen was the idea of PLA in the 90s while the (former) Soviet tank programs still had momentum, and in that time PLA did indeed try to put a 140/135mm onto a tank, but that need soon diminished after realizing that a true 4th gen of the 21st century doesn't only need statistical specs, but a lot of other auxillary abilities and advantages, and needs to be more integrated with the whole ground-air system. Strategic needs are also now no longer inferior to tactical needs for a tank, that's why we always thought weight reduction so important since the idea of a third-gen. I quote the words of Chief Designer of 99, 祝榆生, a well respected researcher: "系统取胜,功能覆盖,新技术先敌应用", rough translation: Win by system, have a wide coverage of functions and use new technologies before the enemy does." That's the systematic battle I've always been talking about, and as you can see from the quote tanks are not designated for some certain function like ATGMs are, they're simply weapons designed to accomplish and assist ground-based assault attacks, along with IFVs. And we also use new technologies to our advantage, which allows for more choices for development in the future. And BTW Mach 6 penetrators are actually not as efficient as the ones with same kinetic energy at 1600~1800mps... Because the higher speed doesn't really penetrate more than the slower one and the penetration dynamics would be more associated with fluid dynamics, and therefore we can't use structural design to our advantage... (Penetration of very high velocity solids can be seen as a fluid so therefore penetration only relevant with solid density) And PLA isn't interested in DU, we don't have so many nuclear waste and we have 60% of the world's Tungsten AND we have the technology to make self-sharpening W penetrators (already used in various munitions) ... There's also no 155mm gun in the world thatt can fire armor piercing rounds, what I talked about was using 155mm HE to anti-tank...