Lore summary
Forsaken Paladins' story rolls out of the Warcraft III campaign Forsaken Kingdom; former paladins deeply mistrusted by other Forsaken, learning to channel the Light in undeath. Their epic mount quest rides 'in the name of Retribution'.
Start-zone changes
Undead Paladin is a new combo: paladins are sent ~level 10 to Bandarion Keep (Whispering Wood, NW Tirisfal) for most class quests; Ruins of Lordaeron dungeon above Undercity.
Confidence note
Official (Blizzard) + Confirmed (multiple credible press, BlizzCon panel/demo)