As everything in life flows in cycle, I predict the search engine that will de-throne Google will be like Google when it started - a simple variation of page rank.
No smarts, no bubble, no signals decided by over fitting to a biased engineer preference.
I wouldn't say the existence of this page proves your prediction right (as it's not dethroning Google anytime soon).
It's easy to forget that the goal of Google isn't to provide a useful search engine (at least not anymore), but the search engine is a by product of them wanting to show ads.
The search engine and the ads are tightly coupled. A better search engine means it can predict with more accuracy what you are looking for and can serve you an even more targeted ad that increases the chance you'll click.
Wouldn't the dethroner of Google be some new technology which is not a search engine like Google but better at solving the original task of finding information on how to solve problems?
Just like how iPad dethroned Windows PCs for average home user but not Mac because Windows had the monopoly and then an innovation destroyed MS in this space and not a competitor.
I don't think Google dethrones Yahoo and AltaVista scenario will occur again.
No smarts, no bubble, no signals decided by over fitting to a biased engineer preference.