As a huge fan of the source novel, I pray a film adaptation can avoid the obvious John Wick style approach and develop a film that captures even a bit of Trevanian’s unique style.
Showing my age but back in the early 80’s Jim Steranko’s Mediascene Prevue ran an article citing Sean Connery’s interest in playing Hel,after Clint Eastwood’s portrayal of Jon Hemlock in Eiger Sanction.
I strongly recommend Trevanian’s novels to any reader of this site.
We’re not old, just seasoned! I wholeheartedly agree with your recommendation and consider Shibumi a nearly perfect espionage novel, although it subverts almost every trope of the genre. It’s a true classic!