If I'm not mistaken, all we know is that all PHB classes should be available on full release and that classes, races and companions will be added throughout EA. Swen said a roadmap isn't planned (which I think is very reasonable).
By the dumbest math, if EA is one year (I expect 1.5-2) and there are 6 classes left, it means one class per 2 months on average (if all are to be added before full release, which I think is likely due to testing). And maybe a companion along some classes or not long after that. Just guessing though.