Development pushes ever on here, and I’d like to mention that the very first build of the 1.7.x branch has been released. 1.7.0-alpha1 is very much an alpha release, with the usual applicable caveats. The major developments are Xlink support for WFS 1.1 and a full implementation of WCS 1.1.1. This release is based on GeoTools 2.5.x.
GeoTools 2.5.x contains the new feature model, which should be able to handle the full complexity of GML and any other model that architects may throw at us. There is still a lot of work to fully incorporate it in to GeoServer, but this alpha release does represent the first step forward towards that goal.