I was thinking the same thing when I clicked on the comments. I somewhat expect this will be the last volume in the series, so one could now hope to buy a "complete" set. I would love to revisit and explore all of the material using modern programming languages.
One might hope that he can at least complete 4C such that volume 4 is complete. I am skeptical that volume 5 or later will see the light of day, But I also cannot predict the future.
This comment made me check the history of the official TAOCP page [1] through the Wayback Machine. Volume 5 was estimated to be ready in 2009 at the very first snapshot (1997), in 2010 by 2003, in 2015 by 2007, in 2020 by 2010, in 2025 by 2015 which is the latest estimate today. At the first glance this looks like an eternal "10 years later", but note that that estimate didn't change since 2015 and the 2025 estimate is now only 3 years away. Does this mean that Knuth does plan to publish anything related to Volume 5 by that time?
