KDE 4.5.4 has been released as a monthly update by KDE team and it has been included by Pat in the yesterday's update (i couldn't access the Internet yesterday, so i missed the news).
I haven't looked on what changes brought in in this release, but i don't think it would be a big one, as this is a maintenance update. Mostly are for translations updates and minor bug fixes.
Several other packages were upgraded as well, as part of KDE updates in l/ directory. KTorrent and Amarok has been upgraded to the latest version as well.
It's been some time since last update to KDE in official tree, but it's official that KDE 4.5.4 will be favoured in the next Slackware release.