Granted, I haven't mustered the courage to begin reading TAOCP, but my impression is it's a timelessly relevant masterwork for the man.
I don't think Knuth is under any illusions about staying relevant: The original editions had code examples for a machine having 6-bit bytes and used self-modifying code to store the return address of subroutines rather than a stack.
In later editions he updated the examples, but even with respect to algorithms the new fascicles make references to quite recent papers and results. The books as timeless as they are, are products of their time more so than most books on mathematical topics.
First example from this new section about satisfiability, the epigraphs:
> “He reaps no satisfaction but from low and sensual objects, or from the indulgence of malignant passions.” – David Hume, The Skeptic (1742)
> “I can’t get no ...” — Mick Jagger & Keith Richards, “Satisfaction” (1965)
Or an example from the text, from a few pages later on:
> “Start with any truth assignment. While there are unsatisfied clauses, pick any one, and flip a random literal in it.”
> Some programmers are known to debug their code in a haphazard manner, somewhat like this approach, and we know that such “blind” changes are foolish because they usually introduce new bugs....
I'm betting "social" and "network" will still be recognizable words in 50 years too.
It might just give the whole work a nice and quaint touch.