Just found this from Nikkei Asia (a sister organization to the London-based Financial Times). Consistent with your guess, they say we won't see M3 until 2H 2023, and that it's is going to be on N3E (the successor to N3)Well, that’s the big question. I have no idea. My best guess is no. Porting Everest/sawtooth to 3nm would likely be no less effort than porting M2. I don’t *think* they would “skip” M2 in the high end products.
But who knows.
I gather Nikkei Asia is a reputable publication, so it seems notable that they're reporting this as fact rather than rumor.
They do get this wrong—the A16 is on N4P, which is a 5 nm process—but then that's a common mistake caused by TSMC's misleading nomenclature:
"In 2022, only the premium iPhone 14 Pro range has adopted the latest A16 core processor, which is produced by TSMC's 4-nm process technologies, the most advanced currently available."