I'm waiting just like you. My goal is to get this Gentoo box moved over to the next Slackware release when it's avaliable. I was just reading the changelog, and it just recently had the 2.6.6 kernel source, and headers added to it. However it has a warning added to it. Something about the 2.4.x kernel is better used for the glibc version that is currently in it.
This probably means this upcoming release is going to be a 2.4.x standard version. So Slackware won't see full 2.6.x support till later. This is speculation on my behalf though.