KDE SC 4.5 is about to be released and KDE SC 4.6 is being discussed. However, Martin Graesslin has revealed some details about what they are planning for KDE 4.7. According to Martin's blog post, they are looking at OpenGL 3.0 to provide the compositing effects in KDE SC 4.7. OpenGL 3.0 provides support for frame buffer objects, hardware instancing, vertex array objects, and sRGB framebuffers. Read more here