In talking with Martin Gräßlin today at XDC2012 in Germany, he shared a brief update on the plans for running KDE on Wayland. Gräßlin, the lead maintainer of KDE's KWin compositing window manager, originally hoped for initial Wayland support by January of 2012 (this was the plan from mid-2011, while the polished support would come much later). In November of last year I then heard the KDE Wayland support would take longer as he idled the porting effort until a stable Wayland 1.0 release.
In catching up with Martin today over lunch, he mentioned that he has been working on cleaning up KWin to make it easier to bring to Wayland, but that it's basically all prep work. There will be the Wayland 1.0 release soon, but still it's going to take a while for KDE to appear natively on Wayland.
KDE developers are working hard to ensure that the transition will be very smooth for users going from running on an X.Org Server to Wayland. Unfortunately, Qt5 is actually setting them back in the porting process. Qt5 has Wayland support and KDE has been making plans for an eventual transition to Qt5. Porting Qt4 applications to Qt5 isn't too bad, for much of the KDE stack, but moving KWin to Qt5 turns out that it will be a very big effort. Martin thinks the Qt5 transition could set the Wayland efforts back by one year.
Long story short, work within the KDE world to support it on Wayland is being done, but this will be a long process and it won't be coming in the immediate future. Martin intends to write a blog post on the matter in the near future where he will share more details.