The numbers 15 races and 8 classes at actual launch were referenced by a couple people as being on Larian's Presskit, but I don't know that for a fact.
The PressKit says "Choose from 15 D&D race & subraces and 8 classes with more to be announced"...but the numbers are probably inverted, as there is 8 races/subraces and 13 classes/archetypes that were announced so far (for the early access).