Gates has some valid points, but the main issue I see is relative to the last "myth" posted at the bottom. The small gap, which may not effect the needs of today or the near future very much, could be allowed to grow because of the current lack of effect. The snowball starts rolling at that point. Ideally we are prepared to face an enemy that hasn't even presented itself so it is difficult to quantify those needs, but we should always strive for supremacy based on intel.
As pressure mounts to decrease deficit spending, the general public will be more inclined to cut the military than the entitlements they have become used to.