I do think that all vehicles should be required to function on biofuels in the future. This is important for the future of our planet and, perhaps, it would put an end to the wars over oil and resources. We do not have a choice here, really. It's a must.
I think that there will be other things that take the place of bio fuels in the future. You can't think that they will be the only option down the road. The people need to stop using fossil fuels,but its going to be a long time before they do that. or we can hope.
I seriously doubt that all vehicles will be required to function on biofuels at any point in the future. Given the exploding population of the planet, using materials that are needed to end world hunger as fuel is foolhardy. We are now seeing a future where the likely substitution for gasoline will be electricity.
I do not believe all vehicles will be required to function on bio fuels in the future. I think the electric vehicles are a much better bet, they just need to be developed and sold at affordable prices. I wouldn't put my money on biofuels since they can be a risk to the food supply.