Apple would have to expect to be heavily constrained to actually do this. Media will rip them a new one for this, and I can already hear the word of mouth that this year's iPhone is not worth buying - pretty much what happened to the 7. They really need some kicker to sell the 14 with the last gen chip unless they discontinue the 13 immediately and start the 14 100 bucks cheaper. That could work. Other than that they need a real kicker to sell this thing.
Those flat camera lenses for example would attract a few people. Every person I know that has a 12/13 is terribly annoyed that you can't put your phone flat on a table even in a case. Or maybe they finally bring back touch ID (in the power button) additionally to Face ID, which is something also a lot of people really want back. OR.... well, they could sell finally offering USB-C instead of Lighting as actually a big feature (and not preempting seemingly inevitable regulatory intervention from us evil Europeans).
No idea, but it has to be something quite substantial if this rumor is actually true. Which it might be, sure. N4 will be crowded. A16, M2 for iPP and MB(A), possibly even the M2 Pro right on its heels (although I doubt that). And I don't think Apple has basically exclusive supply of N4 like they did with N5. Mostly because N3 apparently is a bust until further notice.