KDE 4.6 RC 2 has been released by KDE team as of today. This update will bring fixes for bugs that still lurk in KDE repository since RC 1 has been released few weeks ago. As usual, RC release is intended for developers and testers and users who have the guts of having a small instability on their machines. Don't use it for production use. Instead, use the currently KDE 4.5.4, which i think is very mature and stable for daily usage. I have used this version on my desktop.
KDE 4.6 packages for Slackware-Current should be arriving soon on AlienBOB's KTown repository as soon as he finished building it and testing it. Probably in one or two days, so be patient.
The final date of KDE 4.6 is set to January 26, if there's no major showstopper that would make some delays of the final release.