Orc - Mag'har (They're alredy in the Horde)
Troll - Forest Trolls (Revantusk tribe, already allies with the Horde)
Tauren - Taunka (They're alredy in the Horde)
Forsaken - The Val'kyrs could revive any race of Lordaeron, Trolls, Elves, etc..Am I the only that can picture Sylvanas killing and reviving High Elves to fight for her?
Blood Elves - Hmm, I don't know, maybe some Felblood Elves? They could use the same excuse used with the Highborne and the Night Elves in Cataclysm...
Goblins - Hobgoblins maybe?
Humans - Hmm, they could change some aspects from the ppl of Gilneas and add some of them that are free from the curse as a subrace for humans...
Dwarves - Dark Iron and Wildhammer (Alredy in the Alliance)
Gnomes - Cured Leper gnomes maybe? (Sand Gnomes as an alternative choice)
Night Elves - They missed the oportunitie to create a subrace when they introduced the Highborne back in Cataclysm..Well, they could easly change that...
Draenei - Broken (*-*)
Worgen - Yeah, I'm stuck in this one...
Pandaren - Who cares...