Samsung's still making a flagship line with a stylistic after pretty much everyone else dropped smartphone styluses; and they brought back external SD cards, too, which a number of manufacturers (themselves included) dropped from flagship lines.

It's possible that dropping headphone jacks could become universal, but I don't see any reason to expect it's likely.

I can see wireless charging and waterproof devices becoming the norm.

Most people also buy headphones from popular brands rather than attempt to discern on sound quality.

I see quite a few AirPods and Bluetooth headphones these days. I don't think you can discount the possibility.

If there are enough customers that really want a headphone jack and everyone else was ditching them, it'd be a point of differentiation and hence worth those few cents for some manufacturer to offer one. I suspect that won't happen though because it'll transpire that most customers don't really care that much.