I suspect most ( or all ) ninja schools other than the Infiltrator or Actor will be a subsequent release. Regardless, I seriously doubt the Scorpion will get more than one of the two in the Core. It makes the most sense. I assume Infiltrator based on the beta doc and the BB. Any included ninjutsu techniques will be cursory and necessarily limited in the Core, so as to reserve the meat for the aforementioned subsequent release.
If it were me designing this, I'd probably only have 1-2 Ninjutsu techniques per rank, things that would be universally useful to all shinobi ( 2 ninjutsu techniques at each rank of 1-2, 1 each at 3-5 - universal things like stealth, misdirection, assassination techniques, etc... ). The Infiltrator would be able to buy generic Kata; the Actor, generic Shuji and so on. Indeed, you could fake a Harrier or a Stalker by giving them an iconic school ability and then allowing them to purchase Ninjutsu and some Kata.
The subsequent book should cover things like specialized fighting styles, weapons and tools, gaijin pepper, additional 'generic' Ninjutsu techniques, ninja magic, shadow brands, Kolat, new schools and so on.