I think one thing people are forgetting, is while Barbie is the name of the original doll, Barbie is also the brandname the doll is sold under. So I really dont understand why anyone would assume that there would only be one doll. MAC and Mattel aren't stuipd, they both know they would lose many potential sales from the, "If my race isn't represented, I'm not buying it" crowd. Not to mention both companies are racially inclusive as part of their motto's.
Obviously there wont be a doll representing EVERY race, that would be impossible. But I'm sure it's a safe bet that there will be a white doll (Barbie herself), one of her black friends, and probably one or two more races. I'm betting on an Asian doll, and then some other race. Maybe a Hispanic or Latin doll? Depending on the market, there could even be more.
I'm also quite positive the reason we dont know more about this collection is because MAC enjoys all the extra chatter this collections is getting as people argue over why MAC is only having a white Barbie. The more chatter/excitement there is about a collection the more people who will be rushing to their local MAC counter too see what races they included in the collection. $$$$
Thats also probably why we've only seen the white doll that's a part of this collection. It only adds fuel to the speculation/gossip that MAC is only releasing a collection for fair skinned people. You know everyone who's saying, "I wont buy it if my race isn't represented" will probably be some of the first in line to make sure there isn't just a white doll.