If you have a pack 1+2 fault, it will be no longer possible to pressurise the aircraft.
The residual cabin pressure will leak at a slow to very fast rate depending on factors over which you have no knowledge or control ...namely, the serviceability of the seals on the outflow valves, cargo doors, passenger doors, etc.
Depending on your passenger complement, age group and health status, it is likely that at least some will be stressed merely by the fact that the aircraft cabin in normal cruise is x number of thousand feet above sea level pressure. If the cabin climbs above 10,000 and certainly above 15,000 feet, some passengers will face very serious health consequences if not the imminent threat of death. This is your responsibility and you may face a Court of Law and gaol if you get it wrong.
If you have a pack 1+2 fault which cannot be remedied immediately, you have no choice but initiate an emergency descent using the approved Airbus procedures.
If after you descend and level the aircraft at a safe level of 10,000 feet or MEA, and you are then able to re-establish normal function to the pressurisation syystem, it is ever so simple to climb back to cruising altitude and continue the flight to destination.
But, if you stuff around and dawdle in the descent, thereby causing the pax oxygen system to deploy at 14,000 feet, you now have NO choice but continue the flight at a maximum of 10,000 feet or MEA due to the lack of pax oxygen (already used), regardless of pressurisation system rectification.
As always, if in doubt, FOLLOW the APPROVED AIRBUS PROCEDURES!