I just don't see anyone dethroning Google any time soon. I know how to use google, I know how it likes things phrased and how to find exactly what I want by how I key in my search. I have been using google for nearly as long as I have been using the internet and I think that this is true for a lot of people.
Sites like DuckDuckGo are awesome in theory but their algorithm still needs a lot of work (i.e become google) for me to ever hop ship. I just don't see Google going anywhere for a while.