Technology Review (Jan/Feb 2008) has an interesting interview with Peter Norvig, director of research at Google, where he talks about what Google search has been doing and where it's going.
on natural language searching: "...we don't think it's a big advance to be able to type something as a question as opposed to keywords. Typing "What is the capital of France?" won't get better results than typing "capital of France." But understanding how words go together is important. To give some examples, "New York" is different from "York," but "Vegas" is the same as "Las Vegas," and "Jersey" may or may not be the same as "New Jersey." That's a natural-language aspect that we're focusing on."
Over the next 2-5 years he sees increasing personalization of search results, increasing integration of various types of content, and the increasing importance of delivering information to cellphones and other small devices with small screens and awkward keyboards.