he deal breaker here is the amount of internal volume needed for ammunition. For example the 130/140mm guns in development use enlarged 120mm casings (same diameters) and have ammunition racks that can accomodate projectiles up to 1300mm in length. Thats why their demonstrators you see today have such huge turret bustles.
Not necessarily though.
Take for example the T-55 and the T-62. The T-62 has a larger round than the T-55 but due to better ergonomics, positioning and slightly larger internal volume, it was easier to load a T-62 than a T-55 and the difference in weight between the T-55 and T-62 are neglegible in the context of tanks.
The huge turret bustles are holdover from the Western insistence of using loaders well into now, and now that they switch to autoloaders, they are going for the less radical aproximation which is to use the existing tooling to make tanks with huge bustles with a rather straightforward autoloader solution. You can still fit longer round in carousel autoloader as seen in the T-14 with the main reason the 152mm was abandoned being about the current design not being able to handle the pressure, shortening barrel life to unacceptable levels.
Now, ammunition length is nothing without energy and in this regard recent Chinese research has made breakthroughs regarding propellant technologies (some of those works were shared in this thread pages ago) which indicate that newer 105mm APFSDS can have super high pressure propellant. In other words, theoretically, the 105mm to be used with this "ZTZ-201" can have longer projectiles than 120mm and flying at comparable velocities, resulting in comparable or superior performance even when it comes to KE capability
At what ranges, though?. You need long barrels for that as well, and I don't think it is practical to make 105mm as long as the latest generation of 120mm/125mm guns.
