seconded.
The 12" is a fantastic size for a screen, probably the most usable screen size that is still portable for a laptop. I can't see them doing away with that. Maybe something like 11.6" would still be in the realm of acceptability.
But really, the primary need is to slim down the bezels more. Once you half the bezels, especially the top one, and reduce the size of the speaker grill on top of the KB, the size becomes even more portable. That would make it probably the best general purpose device in Apple's lineup, and probably one of the best computing device of any kind for 90% of the people out there; provided they can replace the headphone jack with a second usb-c.