Today is the day that, had he lived, Coltrane would have been in his nineties. But when Coltrane died, he was in his forties; and in jazz terms he was still considered a young man with a possibility of being active in the future. In 2014, Ted Gioia wrote an essay for the Daily Beast, speculating that Coltrane's recording at Temple University was a glimpse of the music that Coltrane would have possibly made had he lived longer.
Speculative thinking about the destinies of our lost heroes and heroines is common in jazz. We wonder what Charlie Parker would have done if he had lived to go study with Varese; we attempt (through stylistic troping) to recall a sense of them. In this, we are thinking of the future of a spiritual- or philosophically-driven technical practice (listen to the low A-flats that Coltrane intones in "Naima": what is he communicating?) related to black aesthetics.
We are all Afrofuturists when we think of Coltrane.