"[...for much of the next five decades, the U.S. government will be the dominant entity in determining the course of human space exploration.]

Forgive my audacity in disagreeing with the Administrator, but I'd suggest that, right now, we're witnessing the beginning of the end of NASA. I doubt that it's got even two decades left as a meaningful institution in regard to human spaceflight."

I agree and disagree:). First, NASA mission is the exploration of Space. It does this for the citizens of the US {which doesn't exclude the rest of citizens and nations of this world}. The purpose of exploration is to see if it possible that space environment can be of value to Americans, and if so, enable Americans to exploit these things discovered.
Therefore NASA purpose for being is HUGE. If/when the private sector is mining water from the Moon, NASA won't be diminished but instead will grow by a large amount [read: much bigger budgets].

Now you may be right if private sector is launching manned vehicles and having space hotels for tourists, NASA will be less involved in making rockets and building space stations.
But you must keep in mind that NASA is currently involved in improving the art aircraft design- so just because the private sector is making spaceships and "space stations" it doesn't mean NASA becomes uninvolved with human spaceflight. Now, if they didn't help and instead hindered the private sector, then they could write themselves out of it- but even if that happened {and it's not} something like NASA would need to be established to perform the needed govt role in this private sector activity.
And of course, even at the moment or anytime in NASA's history, NASA doesn't actually build rockets and space stations- but instead has varying degrees of management control over this activity. The difference in the future will be markets [the collection of human being interested in the space related matters will be supported directly by "voting with their wallet"] will determine what kinds of thing are done in Space. But even in a highly driven space market there will be things which are more centered in "general good" than individual desires. E.g. a radio telescope on the Moon could more of govt interest, than compared to lunar hotels and lunar solar panel fabrication facilities.

And finally, humans may not ever travel to the stars, but I think it's premature to declare this at this point in time.

"Americans just don't place any value on our country's ability in space. So we're going to end up gutting NASA's science programs only to watch our manned spaceflight effort whither away under budget cuts and public apathy.

It won't be long before China takes the ultimate high-ground. "

Americans have spent somewhere around 400 billion [in say 2000 dollars] on human spaceflight. You can't say Americans don't place any value on this. You can say America place more value of things like National Defense- tens of trillions, but you can't say they don't place any value on it.
As for "gutting NASA's science programs" I think the article debunks that myth.
As for China, it seems it will increasingly become involved in Space activities and within 50 year it may meet or even surpass the US in terms involvement, but within 50 years it's pretty certain that NASA will continue to part *A* major part of this activity.
And of course we aren't even mentioning DARPA.