Natural gas is still current technology. A few decades down the development road it may be considered as grubby as coal. I firmly believe there is far more undiscovered technology out there. I'm no expert but just looking at the rate of tech advances since say WW 2. Who at that time would have envisaged a mobile phone or this mini iPad type of communication?
Someone once said that if aircraft development had advanced as computers have, we would be crossing the Atlantic in five minutes.
Who knows what's round the corner.
The biggest problem is "currently certified". The regulators will screw everything up to the best of their ability.