This should have been the crux of the third act. Marty staring at a photograph of himself that’s gradually fading gayer and gayer.
Also the sequels. All of the movies should have involved trying to prevent alternate gay timelines. Biff steals the almanac, turns everyone gay. Marty finds Emmett Brown’s tombstone, it reads “Died Gay, September 7 1885”
Damn it Zemeckis, so close