Some of the KDE 4.11 features to get excited about include greater XCB usage by KWin, speed improvements for Nepomuk, the initial KWin Wayland back-end, other KWin window manager improvements, lower KDE memory usage, and many other changes. This is also the last feature release for KDE4 Workspaces as its developers begin to focus greater on KDE5.
The early KWin Wayland code is meant to run atop Wayland's Weston compositor at this time. However, KDE will not fully run on Wayland until next summer with the release of KDE Frameworks 5.
More details on the KDE 4.11 changes can be found out via the KDE.org announcement.
For KDE 4.12, the next major KDE Software Compilation update, is to release it on the 18th of December. More KDE 4.12 details will come on Phoronix in the coming weeks and months.