Apple change the main page yesterday.
It must be something big, that Apple change the main page for it.
90 seconds preview. Most likely not, is not great enough for Apple to change the main page for it.
Live stream. No more storing mp3 on hard disk, everything will be downloaded from Apple server. There are people saying that our Internet is still not ready for that.
Beatles on iTunes. This is more or less confirmed, you can refer to macrumors. The four clocks displayed on Apple main page may resemble 4 Beatles members on the album HELP!.
May it all will happened on the iTunes Is just another few hours to go...