tldr- Merging macOS and iPadOS? I don’t think so. iPad app and Mac app parity? I don’t think so. Hybrid? A small possibility.
I don’t see any OS merging happening in the foreseeable future, not because of Apple greed, but because the two OSes simply have two contradicting focuses. macOS was made for the professional in mind (robust and flexible) while making it as accessible as possible to the everyday user. iOS/iPadOS was the opposite—made with the everyday user in mind (simple and rigid) while making it as useful as possible for the professional (and in this regard it is still growing, but it has limited potential due to the OS’ focus). Trying to have one OS do both would merely split the focuses, making it weaker in both extremes. So Apple leaves it to the customer to choose the OS that best fits their uses.
So then there’s the question of form factor and input preference. People got keyboard and arrow input with iOS/iPadOS, so everyone who likes iOS/iPadOS (as is) is pretty much squared away. That just leaves people who want touch input with macOS. The problem with that is it’s likely too small of a niche for Apple to bother revamping the OS and getting developers to jump on board. The reason I say that is because macOS is mainly about professional and power users, and those types of applications are generally not as productive with touch UIs. Prime examples are Premiere (video editing) and Excel (spreadsheets). They require accurate pointing so that you can edit while simultaneously seeing as much of your work as possible. And they have a myriad of functions accessed via buttons and menus. These can be done with a touch UI, but because a finger needs big buttons, there is much more zooming in and out and finding functions buried in submenus. All of this is added time, so those who use these applications professionally would be at too much of a disadvantage if they chose to use touch. This is probably why Apple sees a touch macOS not worth the effort.
That’s also why I don’t see certain professional applications making their way to the iPad, at least not the full versions that exist on desktop, because no matter how fast the hardware is, and even if the OS didn’t hold them back (which it currently does), some applications will be too disadvantaged with a touch UI. Not to mention iOS/iPadOS app pricing issues, which is separate but significant.
I’d note that Pencil input is a slightly different story from touch. Because it is pixel accurate, it doesn’t require a Mac UI change and it can be conducive to certain professional software. But that too is likely too small of a niche for it to be worth it for Apple to put macOS on an iPad, let alone make an entirely new Mac tablet. That’s probably why they made the Sidecar function.
So I think some people understand merging won’t work and pro touch apps mostly won’t work, so they just want a device that can switch between the two OSes and form factors—a hybrid (which the iPad pretty much already is in terms of form factor), so that they can have the robust tools of the Mac and the ease of use and greater portability of the iPad in one device. So far, Apple’s response to that has been ‘why combine the fridge and the toaster?’ meaning do the two actually work well together or do they work better apart? I would say when Macs were Intel-based the two were definitely better apart, but now that they share the same chip architecture, that big technical hurdle has been taken away, and it’s not as clear. I don’t know enough about the underpinnings of each OS to know if there are other technical hurdles. But logically-speaking, there may still been an issue of screen size. Mac’s strength is productivity which weakens as the screen gets smaller. iPad’s strength is portability, which weakens as the screen gets bigger. As of Apple’s current product lines, they intersect at the 12.9” iPad Pro and the 13.1” MacBook Air sizes. Apple did used to have 11.6” and 12” MacBooks, both of which were larger than the 11” iPad Pro, but both were discontinued, so Apple may no longer see anything below ~13” as an appropriate size for macOS. So the ~13” may be the only size to see a hybrid in the future. The only reasons I can see this not ever happening are other technical hurdles I’m unaware of, or Apple just not having enough financial motivation to get around to it.
I don’t see any OS merging happening in the foreseeable future, not because of Apple greed, but because the two OSes simply have two contradicting focuses. macOS was made for the professional in mind (robust and flexible) while making it as accessible as possible to the everyday user. iOS/iPadOS was the opposite—made with the everyday user in mind (simple and rigid) while making it as useful as possible for the professional (and in this regard it is still growing, but it has limited potential due to the OS’ focus). Trying to have one OS do both would merely split the focuses, making it weaker in both extremes. So Apple leaves it to the customer to choose the OS that best fits their uses.
So then there’s the question of form factor and input preference. People got keyboard and arrow input with iOS/iPadOS, so everyone who likes iOS/iPadOS (as is) is pretty much squared away. That just leaves people who want touch input with macOS. The problem with that is it’s likely too small of a niche for Apple to bother revamping the OS and getting developers to jump on board. The reason I say that is because macOS is mainly about professional and power users, and those types of applications are generally not as productive with touch UIs. Prime examples are Premiere (video editing) and Excel (spreadsheets). They require accurate pointing so that you can edit while simultaneously seeing as much of your work as possible. And they have a myriad of functions accessed via buttons and menus. These can be done with a touch UI, but because a finger needs big buttons, there is much more zooming in and out and finding functions buried in submenus. All of this is added time, so those who use these applications professionally would be at too much of a disadvantage if they chose to use touch. This is probably why Apple sees a touch macOS not worth the effort.
That’s also why I don’t see certain professional applications making their way to the iPad, at least not the full versions that exist on desktop, because no matter how fast the hardware is, and even if the OS didn’t hold them back (which it currently does), some applications will be too disadvantaged with a touch UI. Not to mention iOS/iPadOS app pricing issues, which is separate but significant.
I’d note that Pencil input is a slightly different story from touch. Because it is pixel accurate, it doesn’t require a Mac UI change and it can be conducive to certain professional software. But that too is likely too small of a niche for it to be worth it for Apple to put macOS on an iPad, let alone make an entirely new Mac tablet. That’s probably why they made the Sidecar function.
So I think some people understand merging won’t work and pro touch apps mostly won’t work, so they just want a device that can switch between the two OSes and form factors—a hybrid (which the iPad pretty much already is in terms of form factor), so that they can have the robust tools of the Mac and the ease of use and greater portability of the iPad in one device. So far, Apple’s response to that has been ‘why combine the fridge and the toaster?’ meaning do the two actually work well together or do they work better apart? I would say when Macs were Intel-based the two were definitely better apart, but now that they share the same chip architecture, that big technical hurdle has been taken away, and it’s not as clear. I don’t know enough about the underpinnings of each OS to know if there are other technical hurdles. But logically-speaking, there may still been an issue of screen size. Mac’s strength is productivity which weakens as the screen gets smaller. iPad’s strength is portability, which weakens as the screen gets bigger. As of Apple’s current product lines, they intersect at the 12.9” iPad Pro and the 13.1” MacBook Air sizes. Apple did used to have 11.6” and 12” MacBooks, both of which were larger than the 11” iPad Pro, but both were discontinued, so Apple may no longer see anything below ~13” as an appropriate size for macOS. So the ~13” may be the only size to see a hybrid in the future. The only reasons I can see this not ever happening are other technical hurdles I’m unaware of, or Apple just not having enough financial motivation to get around to it.