Somewhat unrelated to your point but the phrase "Google these days" made me think the following: Could Google freeze its index and capabilities every one or two years and make it available as a sort of "search the web like it was in 2008" archive?
That might also solve the problem of how to prioritize search results over time. The people in 2015 are likely to have been interested in different things than the people of 2040, especially for some search terms (vine for example). I mean they already do this by having different search engines for different countries/languages.
Once pressed to give actual examples, we realize it wasn't a trivial search anyways and certainly not something better Google did long ago on a technical basis. And Bing certainly isn't doing much better.
Of course, there are some things that Google does filter out these days like things that seem like pirated content.