The latest release of PyKDE (3.8.0) includes the ability to write KDE panel applets completely in Python -- absolutely no C++ required. This is the first in what's planned to be a number of extensions for PyKDE that allow plugins and related objects to be created entirely in Python; David Boddie is nearing release of modules for authoring KParts for export (PyKDE already imports KParts), KDE Control Center modules, and IOSlaves.
Future plans include allowing QWidget subclasses created in Python to be imported into Qt Designer with complete functionality, and possibly Python scripting and plugins for KDE apps like KOffice and Kontact. The underlying mechanisms and code are similar in all cases.
In some cases, specific .so libs will still be required (depends on the plugin loader), but the Python modules will include autogeneration of the necessary C++ code, along with installers to simplify the task of making the plugins available.
PyKDE 3.8.0 requires SIP 3.8 and PyQt 3.8. While the PyKDE 3.8.0 tarball is available now, it will be several days or more before RPM and Debian packages are available. You can check the PyKDE mailing list for more info.