I'd go with Bing from Microsoft and Yahoo. These two were the search engine leaders before Google came along, and I believe that you cannot go wrong with either one of them.
if google is no longer there,there is other search engines could to choose if other search engines is also no longer,there must be a new technology replace it
If google's no longer here? I'll create my own search engine that will rival all existing search engines
more than likely use bing as microsoft have done a decent job on it, pretty sure aol is powered by google aswell!
probably it'll not happen, but we never know what happen tomorrow. It seems more people choose yahoo.
Every one takes his relevant space on this earth , Google is where he needs to be, its foolish to think negligence of Google, If Google won't be there you won't be asking this questions as we must be having fun with other SE as for now we are having with Google.
There are other sources of traffic than just Google. If you want to run a solid business, do NOT rely on SEO only. My point of view...