Inspired by a recent discussion:
Chazal tell us that someone who says "I will sin and I will repent, will not be given the opportunity to repent" (Mishna Yoma 8:9). Chazal also tell us that there are certain sins for which a person does not have a portion in the World To Come (Mishna Sanhedrin 10:1).
If someone did a sin for which there is no portion in the World To Come, and announced that they were doing it with the intention of repenting later, we can assume that they never repented. Would there be a point in saying Kaddish for such a person?