Sabayon doesn't support plasma active.
It looks like there are some portage overlays that are toying around with it, but mixing something at large as a DE from portage with entropy packages is definitely not recommended. At that point, you might as well go portage all the way.
I see some stuff in the kde portage overlay: http://gpo.zugaina.org/Overlays/kde/plasma-active
But I can't give you much guidance, since I don't see how exactly it is supposed to work.