Bigger sales helps Card sell yet another series' worth of movie rights so he clearly does profit if Ender's Game does well at the box office. (I've seen lots of people arguing that he was already paid so it doesn't really matter.)
Source (has spoilers for movie/book versions of Ender's Game):
http://www.slashfilm.com/enders-game-director-says-new-orson-scott-card-novel-may-power-a-film-sequel/