In a recent interview screenwriter Mark Bomback went on the Q&A podcast and gave more details about an alternative ending of Dawn of the Planet of the Apes.
[there was] a version where you see the arrival of other humans. We had the apes retreating to Muir Woods afterwards, going across the bridge and in the far distance you see a battleship starting to arrive … On a purely character level, it’s Caesar’s story. Why are we leaving Caesar at the end of his story? We want to end on his emotional place, not on a battleship.
It seems the footage was filmed, as a clip of the ship can be seen in an early trailer for the film: