I've been wondering this myself as well.
If we do get them, I think we can only get 2 tokens since you can't prestige in the PC-version of CoD4. And because World at War was not in the steam cloud, which means your progress is only stored on your own PC.
If we do get only 2 tokens, I think thats rather unfair, since console can get 4 max.
In this case we should get 2 for free, however that might be unfair as well because there we're people who didn't even prestige in MW2 or BO.
I can image these are hard decisions for the PC-team.