Lore summary
Shen'dorei: rebels who fled Eldre'Thalas after the War of the Ancients and found refuge in Skywall, where wind spirits anchored their island. The spirits have vanished, pylons holding Zephras are failing. Factions: Windshapers, High Order, Al'Aketh (wiki: Al'Aketh are an Al'Akir-worshipping cult; neutral). Alliance-aligned Skyborne 'pursue the arcane legacy of their ancestors' and gain Mage. New Skyborne druid forms (Bear, Cat, Travel, Moonkin shown; no Tree form seen per Wowhead). New customizations, voices, dances.
Start-zone changes
New race. High Order = Highborne-magister descendants aligned with the Alliance; Mage is Alliance-only for Skyborne (both factions: Warrior, Hunter, Rogue, Druid).
Confidence note
Official (Blizzard) (race, faction split, classes, Zephras Isle, purchase) + Confirmed (multiple credible press, BlizzCon panel/demo) (racials)