The fact that the non-DRMd tracks won't be available in May and the lack of any other announcement today makes me think there will be a May music event.
1. There hasn't been a music event in a while.
2. Steve was noncommittal today on The Beatles.
3. The Beatles and Radiohead are the two biggest acts not on iTS, and both are on EMI.
4.
TV is almost certainly going to get HD content soon.
5. Two big summer sequels start in May (Spiderman 3, Shrek 3), so Apple and the studios would have a good promotional opportunity to bring out the earlier movies in HD.
6. iTunes will probably need tweaks for the iPhone.
7. Apple has another couple of months to get another major record label or two on board with non-DRM music. (Steve hinted that others are in the wings.)
8. If there's not going to be a widescreen iPod until three or four months after the iPhone lands, May would be a good time to bump up drive size in the iPod, nano and shuffle.
9. A May iPod/iTunes announcement would clear the deck for Leopard and hardware in June.