This is a fallacious argument though. It is like saying a horse will always be faster than a car because one can always breed a faster horse. Eventually, it just doesn't work any more. System limits.
Military engineering is limited almost entirely by the limits of materials science. We have come to the point where one can design anti-armor weapons such that no physical material has the strength to prevent penetration and that it takes meters of the best composite materials known to science available for any price to dissipate the energy.
The military R&D effort in the '90s has spent much effort on the engineering of various anti-armor systems that are capable of breaching the fundamental physical limits of armor, and these efforts are bearing a lot of fruit. The US will be deploying new anti-armor weapons shortly that, in the words of the military, "can defeat all existing and future projected armor systems". How do they know this for uninvented "future" armor systems? Because short of discovering new laws of physics and Star Trek technology, there is no known material in existence that is capable of withstanding these weapons. They breach the physical limits of normal molecular materials.
What the US can do now technologically will start showing up in the hands of our enemies in a decade or two. The permanent obsolesence of armor is no more than a decade or two off and the US military knows it, unless we develop a new exotic type of armor/shielding that is not dependent on molecular bonds. As a consequence, future systems are being designed without provisions for protecting against anti-armor weapon systems that can't be practically defeated anyway.