The decision to refloat and repair is not going to be made by Costa or Carnival Corp. It will be made by the insurance company.
I also don't think that decision will be made until they are able to refloat her and see how much damage has truly been done. Repairing the hole is "easy" enough (probably not the best choice of words) and everything that was inside - beds, table, chairs etc etc is replaceable. It's how much damage the salt water has done to the body of the ship that will tell the tale.
It will be priced first - cost of repairs vs cost of scrapping.
If it's repaired I would think Carnival Corp will sell it and it will sail again under a different name, different decor. No company is going to lose any more than it has to, especially an insurance company. They don't have human feelings and even with the losses on this one, money will rule not feelings.