Educating:
Your ending suggestion would've had the movie get slammed even more than it is.
No one wants to see creature rehab, although the book supposedly makes the creatures more human-like and rational than the movie.
I think the movie was long enough. I did feel a sense of cliff hanger at the end. But I honestly did not want to see what happens in the camp. I assume what happens is that she hands the cure over to the military folks and things get back to normal somehow.
I was saddened that Sam died and that Smith truly thought he was the last human alive. For his sake, I wanted the woman to have driven so far to find that the camp had been overrun by those creatures.