A tentative feature list for this next Fedora release can already be found on the Fedora Project Wiki. Some of these features like straightforward multi-seat support were originally targeted at Leonidas but were then pushed back to Fedora 12.
Additionally though, Red Hat intends to introduce liblvm in Fedora 12 to allow user-space applications to interface with an LVM (Logical Volume Manager). In Fedora 12, Red Hat intends to replace nash/mkinitrd with Dracut, which is a modular initramfs generation tool. Instead of using Pidgin as the default instant messaging program, in Fedora 12 the default will become GNOME's Empathy program. The other items on the list right now include the debuginfo file-system and Systemtap static probes.
While not officially confirmed yet, the release of Fedora 12 at this time appears to be targeted for a release in the first or second week of November.