I guess its not going to happen in this decade,but yes it can go down in position but Google is not made to Die.
I think that's hard to imagine because Google is such a robust search engine, but Yahoo! and Bing! are two of many search engines you can substitute for Google and many of its other functions.
I do not see any alternative right now. The one that will replace Google will be my bet for sure, be it Bing, Yahoo or Facebook..
Google can't be vanished totally, maybe only in many years. It have to many buildups in the web, the only way it can happened if web changes it self and the first step is SOPA and PIPA. If it comes to life, it will be disaster for the free web. It will bring web to new stage, where people will start to chose another protocol in alternative to HTTP. There is many alternative protocols even better than HTTP, but no one will accept them at this time before SOPA and PIPA ruined HTTP. So probably Google will be modified but will not be totally vanished ever.
Well, this will surely not happen and if it does then you will be having alternatives for doing so. Also, life does not end if you don't Google for sometime.