Right now mobile ads are cheap because mobile devices are in their infancy. As traffic continues and ads become more advanced they will start getting more clicks. Then they will become more expensive. 10 years ago you could buy ads for as little as 1 cent Now you are lucky to find a .10 cents Adwords long tail keyword. I don't see search engines like big G having any long damage because they will eventually make more on mobile ads. However, I don't see them having a bright short term future either. As a matter a fact, I would say that almost any company that sells ads will suffer in the short term. This includes companies like Facebook, Blogs, and even Hubpages.
As a side note I would also like to point out that Google is one of the better diversified companies in the search engine business. They may not make a lot on mobile ads right now but they make money several different ways. This may hurt them but their competitors will likely be hurt much worse. This may actually turn in their favor in the long run if some of their competitors actually go under or even get bought out by big G.