It seems the trend has been towards later and later recognition, which makes sense given the age of the field and the award.

- Knuth got his for TAOCP in 1976, 8 years after first publication.

- Thompson and Ritchie got theirs for UNIX in 1983, 10 or so years after its introduction.

- Englebart got his for his HCI work in 1997, 30 or so years after the fundamental work was done (but just after its universal adoption)

- Alan Kay got his for OOP & Smalltalk in 2003, 20+ years after the first stable release.

- Cert & Kahn got theirs for TCP/IP in 2005, 20+ years on.

And so forth.