Distributing hydrogen to and within airports will be a rather interesting topic, if this ever gets beyond pretty pictures.
It's probably the easiest to provide water and electricity to airports, and set up some electrolysis plants. Alternatively (if hydrogen sees more widespread use in other industries, e. g. ground transport), expect large airports to get hooked up to pipelines and smaller airports to get supplied by 'fuel' trucks - like it's currently done with kerosene.
Does this mean the A320 replacement has been pushed out until the early 2040s?
RR ultrafan aside, there are no new major engine developments currently. The PW1000 and Leap engines will see continuous improvement but that can be done via PIP's. So no A320neo_neo.
On the airframe side, neither the MC-21 nor the C919 appear to improve much over the A320, if at all. So there isn't much competition there either. As long as A & B manage to keep production and maintenance costs low, they have little to fear.
Boeing may launch a clean-sheet 737 replacement, but efficiency gains (assuming the same engines) are likely in the low double digits. If hydrogen or electric propulsion become practical in the 2030s or 2040s, a kerosene-burning aircraft could look outdated very quickly; like the late piston aircraft were obsolete once jets and turboprops hit the market. So the traditional approach of reusing a fuselage & wing for 20+ years is threatened. I think Boeing will wait and see which new technologies become useful.
So yes, a clean sheet A320 replacement probably won't happen before 2035, perhaps 2040. The only interesting developments until then are a potential A350 / 787 NEO with the RR Ultrafan, and the upcoming fight for the NMA / small widebody market.