It's a good point: can any imagined use of hydrogen for cars even begin to compete with all the other demands for it? They might always outbid the car owners.
For aviation, LH2 has such fantabulous efficiencies that we can expect to see all serious air transport switched over by 2050 (providing civilization doesn't collapse first).
Aviation won’t be using LH2. The volume required makes it not feasible. Not to mention the cooling requirements. Look at the volumetric energy density of it compared to other fuels.
Volume is very cheap on board aircraft, so volumetric energy density doesn't matter. What costs is weight. On weight, LH2 clobbers everything, by a very long way.
For aviation, LH2 has such fantabulous efficiencies that we can expect to see all serious air transport switched over by 2050 (providing civilization doesn't collapse first).