KDE 4.7 has been released just few days ago with many new features, updates, and applications. Read announcements

Kubuntu Backports ppa:kubuntu-ppa/backports has added KDE 4.7 for Ubuntu 11.04 Natty release. So Ubuntu Natty user can update to KDE 4.7 with:

sudo apt-add-repository ppa:kubuntu-ppa/backports
sudo apt-get update
sudo apt-get upgrade

Install kubuntu-desktop or kubuntu-full package if you’re first time tring KDE on your Ubuntu.