This alpha release is the first step towards Mageia 5, which is expected for its official debut towards the end of December. There's much left to do obviously before the Mageia 5 final release, but with this first alpha release a lot of new software packages have been pulled in.
Mageia 5 Alpha 1 is riding off the Linux 3.15 kernel, KDE 4.13.2, GNOME 3.13.3, systemd 208, and other recent open-source package versions. Among the plans for Mageia 5 are to use the Btrfs file-system by default, Phonon VLC as the default multi-media needs, network improvements to Drak tools, upgrading to Samba 4, and numerous other enhancements. The proposed and accepted features for Mageia 5 to be worked on this year are covered via the Mageia Wiki.
More details on Mageia 5 Alpha 1 along with a tentative release schedule for Mageia 5 can be found via the release announcement.