1) Google could add display ads to its SERPs. This would work especially well on informational pages, where searchers may not have an immediate purchase intent but are open to relevant messages.
We’ve updated the AdSense ad code so that it now supports secure ad serving through Secure Sockets Layer (SSL) on Hypertext Transfer Protocol Secure (HTTPS) web pages.
Google clearly has been transitioning to https/ssl search, and now has announced Adsense support for SSL ads. They certainly now have the infrastructure to support display ads on their https results. By using https they certainly can cut out a lot of intermediate statistical snooping (referrer strings and more?), making it even more difficult for the competitors. (Bing copies Google's results?)
It does seem like the best way to restore more organic search results, above the fold, is for webmasters to actively promote other search engines. In the long run this type of competition should improve income for webmasters and ALL search engines, producing a more robust internet.