The Chinese Heroes of the Storm page inadvertently (we think...) leaked the next two characters heading into Heroes of the Storm. The page has since been taken back to the Halloween theme, but not before the image of Overwatch's Hanzo and World of Warcraft's Alexstraza was captured by eagle-eyed fans. This confirms speculation from September that the pair would be joining the Nexus.
Source: Icy-Veins.com