Thanks to Jürgen E. Fischer, GRASS 6.4 available in the
OSGeo4W installer has been updated to the current SVN state.
http://trac.osgeo.org/osgeo4w/
Running the installer updates an existing GRASS-OSGeo4W
installation.
Please test it as much as possible to identify remaining
problems before the final release. Please test the GRASS-
QGIS tools etc.
Besides that, the stand-online winGRASS installer is available,
too.
Markus