How do you think Google can motivate 3rd party advertisers? I'm talking about the Rubicons, Pubmatics, etc. Google doesn't have any real leverage over them. Other than the fact that as publishers do move to SSL (because of the SEO penalty that non SSL sites have) they won't use the SSPs that don't demand or can't insure 100% SSL for their buyers. So in effect Google is putting pressure on them to do it.

I don't understand your next part at all. Who would charge a premium to http only networks? Those sites don't actually rely on Google for delivery.