In the non american world, where "trucks" are not a daily commuter, a sedan is not out of date. Nor is a hatchback, nor is a ferrari. The family wagon, truck and hybrid truck/suv have been an out of date style for the last 50 years in the developed world.
The Ford Bronco was introduced in 1965. The Jeep Cherokee arrived in 1974. I remember seeing a lot of them as a kid, though if I had to pinpoint the start of the SUV craze, it would probably be closer to 1990 when the Ford Explorer first came to market.
There is no commonly agreed-upon definition of an SUV, and usage of the term varies between countries. Thus, it is "a loose term that traditionally covers a broad range of vehicles with four-wheel drive."
As such I am happy to claim, given there is no formal definition of what is and what isnt an SUV; that they dont exist at all, if only wishing made it so.
If one wants to claim they do indeed exist - there are plenty of examples from the 1940s and 1950's. “Sport utility vehicle” appeared for the first time in 1974 in the brochure of the first-generation Cherokee. So by the measure of marketing material, they have not been around 50 years, they have been around 47 years.
And it's not a US thing - the Germans, French, and British are also more and more switching their focus to the SUV form-factor.
Even allowing for the massive definition creep that basically every car where the bonnet / windscreen angle is shallow being an SUV. No - around 30% would be my best guess.
I think Ford, that massive iconic US car brand, have discontinued all sedans in the US now, since they're so unpopular.
pretty sure members of ((the set "truck") + (the set "suv")) have existed for more than 50 years, because that union includes trucks