I think bing and yahoo would have been leader. I tend to think that bing would outrank yahoo. Microsoft it's an old company.
I think Yahoo will be the king of SE by following bing. And SE optimizing for google will doesn't exist.
If google doesn't exist then we're will be not having google to use. So, we may use other things like yahoo, bing etc.
Many of us oldtimers existed before existence of Google. There will always be search mechanisms available.
Use Bing or Yahoo or maybe others that would fill the place. I have seen a few search engines be on top and fall AOL, Alta Vista, Yahoo. Google won't be king forever, once they pile on too much advertizing and pillage user info people will go to the next. The life cycle of a search engine- get everyone on board then start raping and pillaging them for profit. The the big shareholder cash out and the search engine company falls from grace. Life of a publicly traded tec company.
We would be using an alternative, just like with anything in life. What would we do without myspace? Oh ya, Facebook. Same thing with Google, we'd be using bing, yahoo, or some other SE.