One can envision a scenario in which the offender, having confessed and then re-offended, is finally apprehended and then blames the priest: "Well, I confessed to Fr. X and he could have stopped me."  The offender might try to mitigate his own responsibility in that way apart from whether or not he was denied absolution; and again, the priest would not be permitted to affirm or deny whether he gave absolution.

I tend to think, though, that none of this is likely: I don't think serial sex offenders are getting in line to go to confession.