well we've heard what, 3, 4 songs? I don't remember well but if melee is any indication we'll have one song for each game plus other extras thrown in, plus menu themes, adventure mode songs and many others. They've only shown demos so far, and the only song we've heard completely was the one composed by Uematsu for the presentation.
I'd say, hold on to your socks, because when the game comes out the music will surely deliver. They won't tout their list of musicians if they weren't going to deliver something worth of their fame. I don't think an artist like Mitsuda would make a crappy song for the game and call it a day.