Personally, I think 8 classes is the exact right number. But I doubt I'll agree on their breakdown. Ideally I'd want to see
4 Basic, generic classes. Intended to cover most everything.
Fighter, Rogue, Priest, Mage
4 variants on these classes, showing examples of more unique options, with the intention that the DM would use this sort of class to customize their game.
Paladin, Bard, Monk, Psion
the other nice thing being that this breakdown can handle most pre 4E PCs pretty well *(druids being priests, rangers being rogue/fighters and barbarians being fighters)...