I've noticed recently that it doesn't seem like Koji Kondo is composing a lot of new Mario music anymore. Just about every game has a different composer, and Kondo is only credited with "Original SMB Theme." I doubt he's really getting involved with most, if not any, with it. Anywhere that he is credited with the composition of the song (like Mushroomy Kingdom for instance) it's just a remix of an old theme. Take Super Mario Galaxy for example:
Only four of the game's 81 songs according to the SMG soundtrack were new ones by Koji Kondo. They were Good Egg Galaxy and the three themes for the Comet Observatory. All the rest were either composed by Mahito Yokota or were Kondo's old Mario themes arranged by Yokota.