Joe Henderson's my go to comparator. Same concept though - Gradual running out of self-belief in the Concept in the mid 70s in face of dwindling critical and audience enthusiasm, then triumphant traditionalist return in the Reagan era: 'Trane plays the American Songbook, Live at the Village Vanguard (Blue Note, 1981)', 'Night Trane' (GRM, 1986), etc etc. Like Henderson (and Shepp, if you like his later work) they'd probably be good records, but its not an entirely appealling thought.
However, I'm not sure it's right. Coltrane's final period deepening comes at a time when free jazz is still riding high, rather than in the face of gathering indifference and bop revival in the late 70s, as with Shepp and Henderson. So, as always, it looks like he was leading the way into something else.