Further to 42's answer, if we study genetics statistically, where one allele is dominant to another, there is usually a 3:1 ratio of dominant characteristics showing to recessive. For instance, if A is a dominant allele for pointy ears, and a is the recessive allele for not pointed ears, we would get the following combinations; AA, Aa, aA, aa. Because A is dominant to a, the heterozygous combinations Aa and aA both result in pointed ears and only the aa combination does not.
Because this ratio does not exist in elven populations, we can assume that neither allele A or a are dominant to one another.
This leaves us with the situation where ear length must be determined by incomplete dominance, or more likely, a situation where more than one set of genes determines ear length. In these situations, a blend is normally created, where the offspring is an average of the parent genes.
Assuming the rules of genetics hold true in Middle-Earth (which incidently they don't, because a hybrid such as Elrond, Arwen etc would actually be sterile), 42 is correct in assuming Aldarion would have slightly pointed ears. QED.