True, but each of them will take time to design, balance for gameplay, and implement. So I imagine that while we'll probably see a fairly wide array of options, likely much of the stuff from the PHB, they'll probably push some of the more esoteric and/or difficult-to-implement options to the inevitable expansions/sequels simply due to time constraints.
(That's not to say we'll only see PHB options at first - some classes, like ranger or sorcerer, could really use some post-PHB options)
I'd love to see Shadow Magic, Storm Magic, and Divine Soul for Sorcerers, Horizon Walker, Gloom Stalker for Rangers. Because it's so iconic FR Purple Dragon Knight might be in as well. It all depends on how hard it is to impliment subclasses.
For Races I think Aasimar will be in because I think they tie to the BG: DIA book some how, which is why they don't count as PHB +1 for Season 9.