Once KDE 4.11 is out the door, KDE developers can begin focusing much more of their efforts on KDE Frameworks 5, Qt 5, and KDE Plasma Workspaces 2. For KDE 4.11, the developers will just provide bug-fixes, translation updates, and other point release material for a period of two years atop the current generation KDE Plasma Workspaces.
This decision is primarily about the Plasma Workspaces but there could be further KDE 4.x releases with improvements to applications and other libraries. By having the major kde-workspace code-base going into maintenance mode for KDE4, the wait to KDE Frameworks 5 and Plasma Workspaces 2 should ultimately be shorter.
For more information on this decision, read Aaron Siego's blog post. There's also details on KDE 4.11 features.