I had hoped that the Scarlet Onslaught would have been a reorganization of the original order, going back to their basic principals, but new evidence has come to light. As I expected, High General Abbendis will be heading their efforts in Dragonblight, out of New Hearthglen. Unfortunately, all quests involving them involve torturing and killing their members.
HOWEVER.
It would seem that our destruction of Balnazzar has taken much hold on many survivors of the original Scarlet Crusade, and have gone back to the Light, form the "Argent Crusade" with the few members of the Argent Dawn. They hold the position of Light's Hope, a fortified area in Dragonblight. They are indeed a faction, with the newly reinstated "Highlord Tiron Fordring, Grand Commander of the Argent Crusade" as their leader.
May the Light always shine.