Not so easy.
If the manufacturer pulls their support, your aircraft are effectively grounded. Airbus had threatened to do that to the 12 Airbuses 340s that boeing bought back from Eva Air, but thought better of it at the last minute because of the larger number of Boeings they buy back in their deals.
Unfortunately we are not talking about an AD here. We are talking about a modification (An AD is usually an inspection or a repair) which would require an STC (Supplemental Type Certificate) If airbus doesn't play ball then the aircraft are grounded forever.
CHeers
Wino