Is QGIS 2.10 Pisa for Ubuntu/Windows already available?
The Ubuntu/Debian packages for 2.10.0 are already listed at http://qgis.org/debian/dists/vivid/main/binary-amd64/Packages but not yet announced.
Apart from that, you can already compile from source: http://qgis.org/downloads/qgis-2.10.0.tar.bz2
QGIS 2.10.1 is now available for most platforms from https://www.qgis.org/en/site/forusers/download.html. Thanks to the devs for late bugfixing and patience on the user side.