"Macbook" is the heart of the entire PC portable line for Apple. "Macbook"is the grounding of the brand itself.
I think Apple will release the Macbook as the first Apple Silicon machine because of the optics of confidently putting the hardware at the symbolic heart of the entire portable line.
I do not think the 12" that was discontinued should be thought of also as where the machine will be picked up in terms of form factor. This is not how Apple behaves, when tech shifts or they don't like where they left off, they change direction. (i.e. the Mac Pro trashcan -> modern Mac Pro)
Apple Silicon will allow Apple to reintroduce the Macbook as a compelling machine addressing many customer types. This base machine would pave to eliminate the Macbook Air and redesign the Macbook Pro.
With a few models of Macbook and Macbook Pro the portable product line will be simplified and clean up the confusing price / feature / performance comparison problems that exist today.
In many ways the same was true in 2006.
Apple's been consistent about ~10 hours of battery life for a while. They've hit their spec and think that most people don't need more in typical usage. So they'll be able to shave battery volume down to continue their trend of thinner without sacrificing other specs.
The recently discontinued MacBook was a vision statement that the hardware could not quite reach, much like the first MacBook Air. Here, I think that statement realized would be a MacBook Pro that is as thin as that MacBook, and is still notably faster than the current MacBook Pro.