I see two issues:At the moment, I’m not really interested in foldable iPhones. Apple needs to get it right.
For the upcoming years, Apple just needs to focus on using higher-end materials such as high-grade titanium, iron, sapphire glass. This is what will appeal the consumers the most.
Folding MacBook would be awesome. Imagine how convenient it will become to travel with it.
1. If you unfold it to be a large screen you need a way to keep it standing as well as carry an external keyboard. I have Apple's keyboard/trackpad case for my iPad and it worked great; however adapting that sort of design for a 20" display would be a kludge.
2. I can't imagine typing all day on a touchscreen. No feedback unless Apple builds in a haptic capability but even then it's hard to distinguish keys. Some might say - voice recognition via Siri but who wants what the are typing to be heard by every all the time? Would be a mess on a plane or in an office.
Will it be viable at some point? Maybe, although I think the whole laptop concept will have evolved before then. The concept is essentially a folding iPad with whatever becomes of MacOS inside. By the time it becomes viable iPadOS/MacOS may be the same thing.I made a slight change to your post. Someone probably said something similar in the early 80's when the first portable "laptops" started hitting the market. Obviously it took the better part of two decades to work out the bugs regarding "engineering, reliability, quality and usability issues" to make them viable products worth investing in.
As for the old sewing machine portables, they really didn't represent that much of a departure from the existing human interface in terms of look and feel. Only difference wa screen size and luggability.