The best way to answer this French real estate question comes from an English speaking French notary.
He reminded us that the date for when the Act Authentique is signed, remember it is the final contract in a French property transaction, the day you will pay your money and get your keys. This date in the first contract (compromis de vente) is only tentative and can be changed.
Keep in contact with your English speaking French notary to learn if the tentative date may change to become sooner or later depending on the time it takes for certain parts of the contract to be completed.
So like the French notary said “yes, it can change” or maybe it will not.