Just looking at these a little closer, here's the new light tank with the Night Gaunt.
And then the equivalent new medium;
Moving to the new heavy tank, we can see the bulk of the heavy tank, but the design cues are very consistent between the new medium and the old Night Gaunt.
If we move away from the Dindrenzi, we can compare the Night Gaunt to the new Aquan Heavy tank, the Anguta. It's a hellishly large and bulky piece of hardware - see one on the battlefield, you better get out of its way or bring it down as soon as you can!
Speaking more of the Alliance of Kurak, here is the old Valenfyre with the new Terran medium tank. The older sculpt is actually slightly more bulky, but also rather more 20th century. For me, the new model is more futuristic;
Here is the Valenfyre again with the new light tank;
At the other end of the scale, here's the heavy tank dwarfing the Valenfyre.
And finally with the Dindrenzi;
So hopefully that gives you a better idea of what the sizes of the new models are compared to the old, and how they look together for all of you looking forward to fielding veteran units along with the new.