No. They don't need a search engine. They don't have to do everything, and their latest mistake into Maps(although I like their Map App) is evidence of that. They do need to have credible options when a big company like Google starts flexing their muscle in noncompetitive ways.
Maps is a perfect example. Apple wanted Google to provide turn by turn directions for the Maps app on iPhone. Google refused and saved it only for Android phones. So Apple built their own app. It was ok but not as good. Meanwhile Google was forced to build Turn by Turn into the iPhone Google Maps App and now it is the best one out there. Superior to Android. So, was it all a ploy? Maybe.
Google is currently coming under fire for Antitrust issues. "Don't Be Evil. " We'll see.