Well, updated or tossed out, as the case may be.
But we don't give the new theory the same name as the old theory and pretend that the old theory was right (and unquestioned) all along but we just didn't know it sufficiently (as is done, and will continue to be done, regarding "evolution"). We don't call Special Relativity "Classical Mechanics" or "Newtonian Physics", for example; when the new evidence came in which required updating Newtonian physics, we didn't say "look at this new stuff we've learned about Newtonian physics". We said "Look at this new stuff we've learned about the world", and then updated (i.e. altered) Newtonian physics to create a new theory.
That's not what will ever happen with "evolution" though. All new evidence will be greeted with "Look at this new stuff we've learned about evolution", rather than "about the history of biological life". The new data will be assimilated, the "theory" of evolution will be updated or even altered beyond recognition... and then repackaged as "evolution" again. With the result that "evolution" (unlike classical mechanics) simply cannot ever be disproven or proven incomplete, because it's a moving target.
And no, that's not how science usually operates.
The reason for this is that when you boil it down, "evolution" is effectively synonymous with "the history of biological life" in the minds of most scientists. The working definition of "evolution" is "the naturalistic explanation for how life has arisen". Since this is a rather circular definition of a proposed scientific "theory", it's no surprise that it turns out to always be verified.
And no, I'm not complaining about this per se. That's how science works; scientists almost by definition operate from a materialistic world-view in their work. That's ok with me. I just wish so many wouldn't overreact so much and get all in a tizzy just because some people want their theories to be labeled theories. They are protesting too much. Evolution is a theory.
That's a great point. As I understand it most of the "scientific" evidence Darrow presented in defense of Scopes has now been found to be false.