People seem to have short memories. In the US, under the presidency of George Bush Jr., SUVs were heavily subsidized, and sales skyrocketed. People rejoiced because they could get the big, roomy, and powerful "trucks" they wanted at a new, low price. Yay!! Then, when fuel prices rose, these same people cried about how unfair that was, and they wanted the government to "fix it."
We had a repeat of this starting in late 2014 when retail gasoline (petrol) prices started their sharp decline (see XB1 Commodity Quote - Generic 1st 'XB' Future - Bloomberg Markets and click on "5Y" for 5-year timeframe). As retail prices fell, sales of gas-guzzling vehicles rose. People have short memories. They just don't envision their fuel-thirsty 2015 vehicle becoming an impediment, because fuel prices are relatively low today, and they don't imagine that could change.
If in the next week retail fuel prices returned to their mid-2014 highs, you'd see a sharp-decline in fuel-guzzling vehicle sales and a rapid return to more fuel-efficient models. This happened the last time(s) there was a sharp increase in retail fuel prices.
FWIW, when I was shopping for a new vehicle in early 2015, I elected for an Audi Q5 diesel. The SUV form factor was helpful for hauling music gear to gigs, personal comfort (I'm 6'2", 195 lbs), but the diesel engine really shines! My all-time high fuel economy was on April 4/16, 528 miles from Virginia to Florida (USA): 4.54 L/100 km = 51.8 MPG US = 62.2 MPG Imp. That's an SUV, with AWD! I'm No.1 in Fuelly for all Audi Q5s (including the hybrids), and I get better fuel economy than many small sedans. It was a smart move for me, all around (except for that Dieselgate thing :-/ )
So I don't buy into the "death of small sedans" story any more than I buy into the "post PC era" stories. A decline in unit sales does not necessarily mean "the same rate of decline will continue unabated until unit sales reach zero."
2015 Audi Q5 "Progressiv" + S-Line + Scuba Blue, 3.0L V6 TDI
(Highest fuel economy for all Audi Q5s on Fuelly!)