Commercial aviation requires power systems with the very high energy to weight ratios. I can't see any replacement technology coming along to beat the energy efficiency and power of the Jet engine and Jet fuels.
If Diesel/Kerosene ever starts to run short, it would be sensible to reserve this fuel for commerical aviation. Every other form of transport that uses these fuels could use something else. Ships could stretch their use of heavy oils by combining wind and solar power with some heavy oil use. Trains, cars, and probably most leisure flying, could be run on Electricity, only commercial aviation needs diesel/kerosene.
Richard Branson's initiative to certify bio-diesel as a Jet fuel may result in there being another option in case the oil gets too expensive to extract. But I doubt oil will ever be too expensive to extract. And the last I heard was that there was five times more oil in known reserves than would be needed to start a runaway greenhouse effect, if it were all burnt.
Aviation will only be sustainable when the world economy is broadly sustainable. And being sustainable may not be enough. If we don't stop adding to the CO2 and other greenhouse gases in the atmosphere, it's possible that nothing could be sustained, because nothing could cope with the rate of change cause by massive global warming.
I see a massive carbon sequestration programme being our only hope combined with ongoing emissions management to ensure that all industries, including commercial aviation, have to recover from the atmostphere all the greenhouse gasses they emit.
Luckily plants do a great job to capturing and storing carbon.