To be honest I doubt SG was a significant percentage of their revenues.
Yes, veterans would typically spend more but there are only a few of us to support the growth GW needs as a business. If Games Workshop would fail it would be for a variety of reasons, SG not being one of them.
But business logic aside, the miniatures gaming space is seeing some disruption at the moment and I enjoy the pluralism with new companies (e.g. Mantic games, Warlord etc) and all the crowdfunded projects.
We obviously need to embrace all that as a community!