When it happens and The Game sells good enough, maybe the Devs will make a mission pack... What would you like to see there?
I would like to see new races. Now, when the game is tied to wizards rather than races adding new ones shouldn't be a problem, and the number 12 is no longer a limitation.
So, my propositions for new races:
1. Azrac (a great come back!) - sphere: fire, allignment: good (I know they were neutral, but neutral fire creatures are Tigrans, and evil fire creatures are orcs), typical terrain: desert. They would be similar to Tigrans, but I'm sure the Devs can make them original and cool. Some city has to be a source of all these elephants, scorpions, djinns and other monsters.
2. Grey Dwarves - a group created from a schizm among the Dwarves. Sphere: earth, allignment: evil, terrain: underground + mountainering. They could have units like kobolds, spider riders, stone giants, Iron Golems, domesticated Earthworms, like from Dune or smth.
3. Gnomes - sphere: life, allignment: good, terrain: underground/grasslands. They would be a band of magical creatures, not very strong in combat, but dangerous. Most of them would have concealment and lots of movement points. And to balance their really poor combat skills, the gnome warriors could have phasing (now, when it is weakened).
4. Lizardmen (another come back!) - I heard lots of people liked them. I also did. They had a cool tactics of corsairs, attacking the enemy cities and escaping to the sea. I don't think they should have cities on water. This would be strange. Sphere: water, allingnment: neutral, terrain: water. And please, don't give them salamanders!!!
5. Barbarians - less civilized men. They could have armies of berserkers with claymores, zephyrbird riders, mammooth hunters, witchkings. And maybe a wyrm or two to worship them. Sphere: air, allingnment: neutral, terrain: steppes.
6. I don't know... maybe some inscectoid/arachnid race? Sphere: death, allignment: evil. Terrain: wasteland. Creatures like giant bugs, mantis, Big Beetle (without a rider), Nest Queens (with consume ability of the Gluttons), workers as 0 lev units.
Maybe you've got some other ideas for new races?
E.g. some from the original Master of Magic, these beastmen creatures looked interesting. And High Elf? Waiting for more ideas...