Well, the good old yellow pass was apparently only widely used in very few countries, Germany being one of them.
Therefore, there will be a digital Covid vaccination passport from the EU, there is already one from IATA and so on. But yes, a swift vaccination effort can yield substantial revival of air traffic, as already visible in the USA and domestically in China (back to 100% pre-crisis level since October). There is a lot of pent up demand for vacations outside of your own home, and actually a lot of pent up spending as well, as people could not spend their money during the pandemic.