For how long after the last A380 delivery does Airbus have to provide spare parts for it?
When a company decides to terminate the construction of a specific airplane, then this company needs to follow some conditions. In the contracts between Airbus and airline companies, there are many conditions concerning multiple aspects.

There are conditions for example about:


spare-parts availability
transfer knowledge about specific features of the airplane
training (not for all the occasions)
and more (we are not in a position to know them all and in detail)


These conditions are discussed in the beginning, before the signing of the contract. Of course, conditions may differ from one contract to the other, but I think you got the point behind this idea.

So there is no way that someone will tell you what will happen between Airbus and their clients because this information is confidential. As soon as, the clients of Airbus do not sue them, then their contracts are including mechanisms about this.

Lastly, these contracts most of the time are including basically conditions about safety or financial sections. There is coming the role of ICAO, IATA, EASA, FAA and more. These organizations are responsible for managing properly also the sector of safety/security. The fact that spare-parts availability is playing vital reason in the safety of the passengers among the world, then it is 100% sure that they also know about it and they know how to handle it.

Hope that I helped.