Arguments for why it might be Shanks the Yonko: The last time we saw Shanks in the manga, he was in Elbaf, and for a Gorosei/Holy Knight to teleport, it’s heavily implied that someone has to be there to teleport them. So, Shanks could’ve been the one who allowed the other Holy Knight to teleport.

Arguments for why it’s not Shanks: The character doesn’t seem to have a scar (but the part of the face with the scar is hidden) Oda is definitely just trying to create suspense.

Overall, I think the odds are pretty even