I think a 4" iPhone 6C is plausible. If Apple were to build it, I would be shocked if it were to not include Touch ID. I would be surprised if were to not include NFC, because it would be stupid to not include support for Apple Pay. That makes the A8 chip the logical choice, even if the camera and flash might be taken from the iPhone 5S.
I used to buy a new iPhone every year. I skipped the iPhone 6 because it is too big. I very much want Apple Pay, but I'm not willing to accept a phone bigger than my iPhone 5s. I prefer the size of the 4s, but the 5s is tolerable.
Zuckerberg is deceptive. While it's true that the interests of Apple customers and Apple Inc. are not perfectly aligned, they are much more closely aligned than the interests of Facebook users and Facebook Inc. Tim Cook's point about Apple not having a financial interest in selling Apple customer's privacy is well grounded. Facebook's business model is selling their users' privacy to advertisers. Selling privacy to advertisers is Facebook's only source of revenue.