Volvo recently demonstrated a five-cylinder vehicle with two fuel tanks that can use gaseous (a hydrogen-methane mix or natural gas) or liquid fuel (ethanol or gasoline) fuels. 
The aptly named Multi-Fuel features an engine that can automatically detect the fuel input and adjust itself appropriately, according to Edmunds.com's Inside Line.
While more vehicles are likely to accept multiple fuels, this is taking the flex fuel concept to the absurd.
We may see the automotive industry become even more regional as vehicles will be tailored to the available resources in efforts to reduce dependency on crude oil.
Nations that have higher availability of natural gas will go that route, Iceland will likely standardize on hydrogen vehicles, agriculturally rich nations will opt for biodiesel and ethanol power and the U.S. market will fragment as flex fuel vehicles will be more popular where e85 is readily available. This is a nightmare for the big auto companies, but provides opportunity for smaller players.
