If the Jewish Temple was rebuilt then a High Priest would need to be appointed and they would have to be a true genetic descendant of Aaron. They would also need to have Cohen status in the orthodox Jewish Synagogue. Today many who claim Cohen status have different y-dna such as J1, J2 and E-M215 as well as R1b and R1a and others.
As I have demonstrated elsewhere Cohen J1 and J2 are of Ishmaelite Samaritan ancestry not descended from Aaron in the direct male line. E-M215 is of Javanite Samaritan ancestry on the direct male line. In fact the true priestly line that has remained among the Jewish people is R1b L584. There are also many R1b L584 found among the Assyrian and Armenian Christians who descend from the numerous priests who the New Testament states embraced the Christian faith.
Yeshua or Joshua the son of Jehozadak who was the first Jewish High Priest after the Babylonian Exile was most likely the founder and ancestor of R1b Z2103 L584. His son the High Priest Jehoiachim or Joachim was in the time of Judith and the Babylonian King Nabonidus the Assyrian.
However only a High Priest (Kohen haGadol) can be selected from those of a lineage in which there have been no marriages with converts, divorcees or gentiles. A High Priest may be appointed by the Sanhedrin and the King or just by the King.
Some believe the third Anti-Christ (possibly of N1c-L666 y-dna of the Tribe of Dan) may rebuild the Temple and appoint a false High- Priest (probably a Cohen claimant of J1 or J2 y-dna). He will be defeated by the Great Monarch of Davidic (R1b L21 y-dna) lineage who may appoint a High Priest for the Jewish people of the true Aaronite lineage of R1b L584 y-dna.