Actually, if you look closely at all the product in the marketplace, synthetic polishes have overtaken carnauba waxes by a large margin. There simply aren't very many carnauba-based products on store shelves any longer. Next time you're at Pep Boys or a decent auto parts store, do a mental inventory of synthetics vs. carnaubas.
Carnauba products have always been pricey but the thought process was that they lasted the longest so that somewhat justified the price. When chemists finally developed a synthetic version of carnauba and did it cheaper than adding the real thing to car polish, the end of carnauba-based products was at hand.
Polymer sealants have been around for as long as I can recall. Who remembers Polyglycoat? But it's only been in recent years that the sealant category has expanded. Good timing for them; the car care products industry has been growing substantially since the 1980s.
As long as there is a price advantage to synthetic polishes over carnauba, you won't see a comeback of carnauba. I think the product type will always be around since there is a market for it until regulations push the price of carnauba so high that most every product mfr drops it from their line.
On the subject of motor oil, I'm not sure there is a balanced correlation to car polish. Motor oil has to meet various global standards and mfr requirements whereas nothing even remotely resembling a standard exists in car care products. I have a 9 page report from Unocal detailing the test requirements for API SL/ILSAC GF-3 service category and the impact of these requirements on motor oil formulation. The EPA plays a big part in the improvements in motor oil in terms of exhaust emissions and CAFE requirements. Nothing of the kind exists for car polishes.