Hi
It was not known to us, and not so visible on the Xilinx Web, but:
Vivado ODD releases are where Xilinx does add more new features
Vivado EVEN releases should be "more stable" and customers should try to use EVEN releases
Petalinux releases are always aligned to EVEN releases of Vivado
This is what Avnet has said on public forums.
Info from X-Fest2014, Vivado 2014.4 projected release date 18 November. Release date for Petalinux 2014.4 not known unfortunatly, hopefully it is aligned with Vivado release.