Mark Gurman seems to think it's happening.
I bet that the Touch ID for macOS using iPhone is just a compatibility measure for older hardware, and not the main thrust of the feature. Just like how Apple is now working on Force Touch alternatives for older devices. Obviously, they will not pre-announce macOS with support for built-in Touch ID without hardware to go along with it.
I think the same goes for Siri. Clicking a dock icon seems a tad clumsy; it takes you away from the content. Tapping a button on the touchbar would be better and more seamless.