And that's the danger. Not that the "teaching" will ever change (you'll always be able to find it in the internet-searchable Catechism) --- but it will simply be a dead letter. Nobody will say anything. Like nobody says anything about contraception. Silence conquers all.
I have not read that book yet, but from his discussions about it, he believes that Jesus clearly often stated that many will sadly be lost.
We do not know how many pointy skulls of bishops will line the blazing floors of hell, but I think it behooves our Bishops to seek to perfectly align all their teachings with the teachings of our Risen Lord, and not try to weasel their way into popularity in today's warped and sinful culture, leading untold numbers of other people astray.