New Ways to Monetize the SERPs

For a very long time (at least in web years), CPC advertising has been the only model for search engines seeking to monetize their search results. While the effectiveness and profitability of these ads can hardly be disputed, it's also obvious from statements like Google's famous "20% of all queries each month are completely unique)" and Ask's "80% of our users' searches show any ads at all" that hundreds of millions of searches are currently completley unmonetized.

I think it would be naive of us to think that this practice can endure indefinitely. For any other page/site on the web to receive the level of traffic and eyeballs that SERPs pages do and remain unmonetized is almost unthinkable. In my estimation, it will be months, not years, before we see one of the major three start to use these un-monetized SERPs to run advertising of one type or another.

Any thoughts on how they'll do it? When they'll do it? If they'll do it?