Since 2009 I've owned a "clean diesel" VW TDI. Little did I know.... I bought it with good environmental intentions, and for 18 months have been the butt of jokes about black smoke emissions.
One of the things which will more and more harm GA as we know it now, will be the public perception of the "special few" who bimble around recreationally burning 40 - 70 LPH of highly leaded gasoline, with horribly inadequate emission controls. There will be little public tolerance for polluting like this for fun. As a specialty fuel, it will become more and more difficult to obtain for us. Yes, we'll have electric 'planes, but few recreational GA fliers will be able to afford them.