Of course. If history has taught us anything, it's that no company, product or individual has ever remained 'on top' for eternity. Everything gets superseded and replaced by something better, it's just a matter of when that happens rather than if.
As for search in particular, yes again. There are plenty of ways a search engine could work better than Google. It could read your mind and figure out what you intended rather than having you try and write out your search query.
It could actually answer questions in purely conversation English (or any other language), like what Ask Jeeves tried and failed to do years ago.
It might have results somehow tailored to your interests in a much better way, and basing what comes up on both people/sources you trust, relationships between them and new pages and your exact intentions.
Heck, it could just be better at finding generic pages than Google is at the moment. I'm sure you've come across tons of situations where you searched for a certain specific technical term, right? And then found all the results were ones that only had the most vague similarity to what you wanted, with the term you cared most about it in grey and strikethrough form underneath the result? Even a search engine that realises you want a certain term in a certain context (say, a discussion, or a long form article) would do better than Google at the moment.
So yeah, there will be a better search engine at one point. Quite possibly one that completely changes how searching works in general and finds results that are far more accurate to what you actually want than anything available at the moment.