These numbers would continue to trend down rapidly with industry adoption of improved fertilizer recommendations, which are readily available for implementation. Hurdle is that people refuse to except the data and rely on outdated and wasteful methods of nutrient management. So, while we are trending downward it may not be fast enough.
N and P are the two elements of concern when talking about water quality. There are no federal drinking water standards for K.
Trending down fast enough for what? Innovations keep on coming. People may be slower to adapt/adopt but the "market" tends to sort itself out.