I dont think this device's primary intended purpose will be as a macOS touch screen device, for the many good reasons people have stated in this thread.
apple has been purposefully and strategically slow to develop its touch screen devices - because of the difficulties involved, but probably also was unsure how to maintain its multiple revenue steams. it didn't want simply to have its touch screen devices replace keyboarded devices and result in a less capable product before they are ready.
two things have happened.
it separated iOS from iPadOS. this augurs more powerful iPadOS systems will be forthcoming, with more and more features.
and, just as important, it has now released two wonderful and innovative keyboards, with built in trackpads, in close succession for its iPad ranges.
as i said, I dont think this device's primary intended purpose will be as a macOS touch screen device.
i think it will be either of these two intended devices:
1 a dual OS device: capable of either iPadOS or macOS - user configured, that can be used as an iPad when detached from a keyboard, or use macOS when needed and attached to a keyboard. this is a bridge solution for a few years.
or
2 an iPadOS device that simply uses a more mature version of iPadOS and has a fixed keyboard that is non-detachable from the screen. this is practicable after iPadOS is more mature and able to handle even more powerful business type functions that many people find they currently prefer macOS for right now.
from apple's viewpoint, and profitability going forward, i imagine that even as much as macOS is a heritage system that has great emotional significance, apple wants to get on with new revenue streams such as AR and selling software for self-driving vehicles. getting to the point where iPadOS can be a legitimate replacement for macOS is the point they will want to get to. i think very soon.