From a submission made this morning, tiling support is being stripped out of KDE's KWin.
The reasoning for removing KWin window tiling support isn't because something else has come along that's better, but rather the support was unmaintained, the original developer isn't interested in taking up the maintenance, there's some bugs/limitations (like no multi-monitor tiling support), and the code is getting in the way with other KWin work.
Developers plan to provide window tiling support for the KDE desktop through a KWin script, but there's nothing completed at this point. If it's not done, then KDE 4.10 will be without support for tiling windows on the desktop. This change to KWin will not affect the soon-to-be-released KDE 4.9 that's already been branched.
Thanks to "markg85" for this notice.