We haven't seen the end of the fuel price rises by any stretch of the imagination, and its unlikely they are going to ever go back to the price levels of just a few years ago. This may have a significant impact and colour future prospective buyers view of gas guzzlers. Whilst sales of new large engine cars for business use may still be around for a time, once they pass on to the second hand market for many such vehicles the prices drop like a stone due to the large running costs.
Further we may start experiencing the 1970's style (oil crisis) rejection of large engine cars repeat itself, especially as alternative fuels and smaller more powerful and more economical petrol engines will be developed to achieve the same performance levels. Add in the potential for difficulties with parts supply for more sophisticated aging electronics and reducing support from the manufacturers for older models, a recipe for potential early obsolescence.