Point taken. As you say, 'Air' now means something to the consumer (i.e. light and mid-range, 'good enough for most people' etc.), but it's a terrible name in terms of making Apple's product lineup make any sense.
Apple will absolutely release 'A' SoC Macs.
What will they call them? Will they just be 'MacBook'? That's Ok, but what about the Air?
Riffing on your example, how then would you describe the difference between the Air (I assume it'll be intel powered until it's EOL) and the new A class MacBooks to the average consumer?
And what about the 'iPad' i.e. the most basic iPad? Now let's assume that the new 'MacBook' will not be basic. If not, the naming scheme will just not make much sense across the lines.
I assume though that eventually the line-ups will make way more sense in time as Apple transitions away from Intel in Macs.
Mind you, this is the company that just launched the XS, XS Max and XR... And the iPad Air!
Unfortunately, we're in a transition period. Apple does not update each and every one of their products at the same type, so we're going to get these types of discrepancies from time to time.
At this point in 2019 MacRumor's Buying Guide is listing the iPad, iMac, MacBook, and the Mac Pro as 'Don't Buy'. The MacBook Pro as a caution, and the iMac Pro as a neutral, so half of Apple's line is currently out of date.
As for categorizing, there are always exceptions, but a poster on this board describes the MacBook as generally, a device for the casual user, and I'd agree. It's the device both for the executive that only uses it for business trips, and your aunt and uncle when they load up the mobile home and take off for a one month trip to Florida.
Students, pros without heavy computing needs, and someone who just wants a computer? MacBook Air. Need more power? MacBook Pro.
The iPads are a totally different beast and where the action is. The new iPad Mini is more powerful than my iPad Pro 9.7" from 2015. Assuming the base iPad also gets an updated CPU this year, each one of these is a computational monster that can run anything in the App Store equally as well as the other. And I really think that needs to be emphasized - almost all the iOS devices are equally fantastic, equally capable devices.
We all may have our preferences, but if you are looking to purchase an iOS device, you really can't go wrong.