Not sensible at all. Being on the same processor architecture doesn’t mean the position within the product lineup will magically transform.
Macs and iOS devices do different things for different use cases; their strengths and weaknesses are as much tied into their hardware design as software. People love Macs because of what they can do; Apple, too.
Apple couldn’t force people to use the Mac App Store even if it wanted, knowing how few of the biggest Mac apps outside of the larger software companies (Apple, Microsoft, Adobe, etc) actually distribute with it.
The only convergence we will see is the ability to run iOS apps on macOS, and even then that is merely a stopgap effort; any iOS apps that want to truly make the transition to the Mac will be updated as Catalyst apps. Catalyst apps are Mac apps through and through, despite their use of iOS’ UIKit.
See also: speculation in The mid-00s that Apple would drop Mac OS X for Windows during the Intel transition. It was just as devoid of factual basis then as fear-mongered “sensible speculation” is today.
