All the damage goes through. When something with trample is dealing damage, it only needs to deal lethal damage before going onto the next target. Since there's nothing in front of it after AEtherling exiles itself, it needs to deal 0 damage to assign lethal to the blockers. Since there're no more blockers, all 15 damage will go through to the defending player.

However, trample allows the attacking player to assign lethal damage to each blocking creature before assigning the remainder to the defending player. If there are no blocking creatures (either because none were declared or because they were all removed from combat), then the attacking player can assign all of the trampler's damage to the defending player.




No Trample