I look at it this way:
Turner, Adams, and their ilk had the advantage of being the first generation of professional historians employing German-imported empirical methods. Their work was certainly brilliant on its own merits, but it also holds the place that it does for being at the foundation of the intellectual world in which we still live.
Later, historians from the mid-twentieth century, whether of the progressive or consensus schools had the advantage of being both the first great critics of the first generation of American historians, but also all the advantages of America as an ascendant world power.
What we share with these first revisionists is that in the effort to say something new, we, like them, aren't likely to uncover an incredible amount of new evidence (at least from archives in the United States).
Nevertheless, contemporary events, ideas, worldviews, economic opportunities, and morality will always contribute to the creative energy of the historian seeking to write "history as it actually happened" (or whatever revision on that old line you prefer...). That, combined with the jet-age opportunities for research that could not be imagined in the late nineteenth century leaves me unconcerned that we are running out of things to say.