Apple (or anyone for that matter) doesn’t need to add a new technology to enable the future of payments and sharing. That future is already being invented with wi-fi and cellular data and is way better than anything that could be done with NFC.
People complaining about the iPhone’s lack of NFC remind me of people complaining that the first iPhone didn’t have a plastic keyboard. If software can achieve 90% or more of the intended result, what’s the point of unnecessary hardware?
My hunch is that reliable indoor LTE connectivity is more important for any sort of mobile payments or retail services than NFC. Whenever I ask a merchant how they like their Square, the most frequent complaint is that the wireless signal is too flaky — not that swiping a credit card is too much work.