On adults, however, the Church has not been accustomed to confer the Sacrament of Baptism at once, but has ordained that it be deferred for a certain time. The delay is not attended with the same danger as in the case of infants, which we have already mentioned; should any unforeseen accident make it impossible for adults to be washed in the salutary waters, their intention and determination to receive Baptism and their repentance for past sins, will avail them to grace and righteousness.
Granted, it is possible, but is it probable for an unbaptized adult to even desire baptism much less repentance for their past sins thereby attining salvation when many of the holiest saints were terrified of death for fear of hell?
While it's possible, the odds are too great against it and the price too high.