In concurrence with Christian's criticisms of the film's ending, I saw at the time of the film's release a missed opportunity for resolving the story of the boy and his mother in a way that ties into the fate of humanity. In the film, the evolved Mechas want David not to say anything about the past to the version of Monica whom they bring to life for a day. So, he doesn't. I wanted to see what would happen if he let something slip. I would have her memory return not only of having abandoned him, but also have her retrieve memories, from the same database to which they had uploaded David's memories of her, of what happened to humanity in the interim. She would realize the horror not only of her actions but of the related actions that let to humans' extinction. She would make a heartfelt apology to David and urge him not to die because of her but to 'go on' (hence the song lyric) representing what could have been if his creators had taken more cues from their creation.