There won't be a spin or inclusion of packages simply because that means the package maintainers would have to keep track of the old plus the new gnome and gtk dependencies. There's also uncertainty as Mate is now developed by a much lower number of devs. For a window manager, that's fine, but for a full desktop with lots of components, that's going to create a lot of problems in the future.
In the meantime, if you want to install Mate, you'll have to use their repository:
http://mate-desktop.org/install/#fedora