At least plain URLs can be manually passed to the internet archive for a lookup, but I'd love if publishers/authors made a habit of maintaining their source links (via shortlinks, published errata, etc).
That said, even with how easy it is to update, Wikipedia suffers from this immensely. I can't count how many times I've tried to track back a source from a wiki and end up with a 404.
Furthermore, archivist is a full blown profession with its own professional society. I’m sure IA will always be able to hire people who are serious about preserving and cataloguing information.
I wouldn't be shocked if, if IA is around in a few decades, they start expanding into educational partnerships to ensure the vision continues. Or institute fellowships. Or they may just inspire more people; IA's work was one of the things that convinced me to pursue an MLIS (as a girl, I was discouraged at the time from CS). Or we'll start seeing more degree specializations that mesh the two, like HCI concentrations.
Yes, that's really frustrating. I often have the situation where I click on a reference for a claimed fact and get redirected to the front page of a news website.