We're forgetting the other potentially challenger to Google's throne, at least going by the media. Facebook. Although currently powered by Bing, it's often discussed about them moving in to do web search themselves. Aside from sometimes searching and adding a friend/colleague/family member, I don't personally use Facebook's search, as it's just natural to type in Chromes address bar ("omnibox"), or go directly to Google, when searching. I would find it hard to take Facebook seriously anyway, especially the crap posts they "promote" (as of potential interest) in my news feed and so-called sponsored posts, etc. However, maybe people who use FB a lot would switch over. So, while it probably couldn't overtake Google, it might have a chance to eat into market share of the so-called "big three". (Maybe get 5-8% of it.)
LMFAO what world do you live in? The only reason anyone should be using bing is to look at porn , thats where google faltered , and thats why bing gained so much ground since the "safe search is a must" creed went into effect on the NA google server. Read all about the mistake change here http://theorderoftheironphoenix.com/wp/google-safe-search-fails/ , anyways people can just google videos , images are a thing of the past.
I can't imagine Bing over taking google. I heard a news report that apple is signing a deal with google to have it as it's exclusive search engine.