I want to ask if we're gonna see a version of Ubuntu such as Kubuntu for example but with GNOME shell and not with Unity ? A version called something like Gubuntu. Thanks in advance for your answers :)
Such a release is possible although I think you mean with Gnome shell or the "Gnome user experience" which is also known as the Gnome OS as pushed on future versions of Fedora and SuSE.
There probably won't be a Canonical paid for release, but the community is much bigger than Canonical anyway so it's about getting together all the right people to do it.
I think as soon as there is a set of dedicated people around Gnome Shell and the rest of the UX, there will be an Ubuntu spin on it. I'd call a good release by 12.04 since Gnome Shell is also still in the process of being made.
Would you like to be involved? See the derivatives team for more information:
Packaging will continue on the gnome shell pieces so that the desktop is available all the time, I believe there are ppas.