If anyone is curious of the work or wants to participate, we are
working there: 
https://git.guix-patches.cbaines.net/guix-patches/log/?h=wip-gnome-40

The branch is based on core-updates and we will rebase it every now and
then, as well as merging patches to official core-updates as we feel it
is necessary.

cbaines gave us access to the git repo, it's not official so it's more
flexible, right now the access cbaines gives is all in and trustful,
but in the future they plan on getting branch access control with 
https://gitolite.com/gitolite/ so that people can be given access to
wip branches with associated continuous integration infrastructure for
development.

If anyone wants to participate, please reach to cbaines about access.

Léo