The current search engine market share of Yahoo is about 2.4% and Google's 89 %. Do you think that the wheel will spin over? When you think will happen?
As long as google provides a better product, they will continue to generate more business. I remember 10 years ago yahoo had a close market share with google, but now things have changed. Yahoo's business model relies now on other thing such as expanding into different markets. These would include news, apps, etc.
i dont see it happening anytime soon. however, it can spin over for you if you are nowhere on google and #1 on yahoo!
I also don't see it happening in the short term. But I do believe Google will continue to lose some market share as some people are unhappy with Google.