IMO, there is no point in getting more compression out of songs. Codec programmers should work on better sounding quality codecs. Formal introduction of the sourround sound would be nice too. But my dream is that music begins getting released in its individual track layers. ie the vocals, bassline, rhythm, melody would all be on different tracks and customizable. Of course this could cause copyright problems and abundance of remixes, it would really help the avid audio freaks to truly control and equalize their music.
I'm also waiting for DVD-MP3 players. That way one could burn a DVD disk filled with MP3s and use that in a car.