I don't think he (or anyone who's produced a work of art that massively popular, for that matter) is expecting to trump his earlier success.

Most people who make great independent games (Persson, Daisuke Amaya, John Romero, ...Terry Cavanagh?) originally do so because of a desire to make games, which supersedes the desire to make hits. I don't think notch is trying to top Minecraft. I think he really likes making games.