Last September plans were expressed with a road-map to release Xfce 4.12 in mid-March. Xfce 4.12 was possibly going to be ported to GTK3, but a full-port to GTK3 was decided later on to not be feasible for this release though some packages may be friendly towards the updated tool-kit.
In January it looked like Xfce 4.12 was still moving along. However, development didn't advance as originally scheduled and now there's no release per the original schedule.
An Xfdesktop 4.10.2 point release to the 4.10 series was released yesterday, but no 4.12. The release behind schedule was noted on the developers' mailing list earlier in the month with no "pre3" release (originally scheduled to happen in February), but no new information has been communicated about when this release might happen.
On a positive note, at least development is progressing. The Xfce Git area shows that many packages have been seeing commits in recent days and even hours. When new Xfce 4.12 release information is passed along, it will be shared on Phoronix.