You need to realize Google is not just a search engine. For the most part they've diversified into other online markets (YouTube, Email, News, Maps, Phone OS) that even if they don't exist in their original search engine format they will be around. Even when a product they launch is a failure (Google Buzz anyone?) it barely puts a dent in them.
If anything, Google is getting stronger everyday. Soon they will have pretty much all the information about our lives aggregated and ready to search through haha
Google may have radically changed search, but they're far from the starters of the internet. Similarly, Facebook might have changed social networking, but they wre far from the first social netwrok and far from starting the net. Don't you remember myspace...