Now that I think about it, the Apple // couldn't be a truck either.
We didn't have that with the Mac, but eventually got there. I mean, there's nothing in the list you provided that absolutely couldn't be done on the iPad. Once there, then the utility for the Mac will have evaporated.
I'm just saying, someone sitting in front of a Mac, thinking it's forever is very similar to someone sitting in front of an Apple // thinking IT is forever. Based on the way Apple operates, it's a safe assumption that they will do what they've done before, improve the feature set of their current system until what it CAN do far outweighs what it CAN'T do, then they get rid of the older system. We saw
some of this with the OS9 to OS X transition as well. Features were added to OS X until using it was worth some of the lingering pain points, then they gave the axe to OS9.
I'd have no problem with a replacement for the Mac, like an iPad or something similar or even something completely new, provided it could do
at least everything I can do with my Mac now (and, sure, more would be even better). I don't need a huge screen for what I regularly do, so the current iPad sizes would be fine. I mostly write, do many spreadsheets, give Keynote presentations, and do an occasional not-too-professional movie - and, of course, the other usual computer stuff like email and browsing - so altogether my needs are pretty pedestrian.
The hardware would have to include a real keyboard, or a solution with all the touch and feel and functions of a real keyboard. I could possibly get used to a somewhat different feel, but the flat-glass of the current iPad/iPhone doesn't do. I prefer a trackball rather than a trackpad, and I need it (it could possibly be built-in, as it was on one of the earlier Macs), and I'd be unhappy without it. I need to be able to attach things, like my external backup drives and a CD player, and I'd be unhappy if I had to buy dongles, and have to give up an otherwise needed I/O slot. I don't need great sound, but it should be good enough. It would need to have enough storage and enough RAM to allow me to work reasonably efficiently. There may be more I haven't thought of off-hand.
The OS and all the other software I use would also have to be able to do all that the MacOS can; again, at least as much, as least as well - and more would be better. iOS can't do that so far.
So, bottom line, if the Mac were discontinued, only to be replaced with something better, I'd probably love it. But AFAIK so far the only such so-called replacements are vaporware - for me, at least.
If anyone out there can tell me that I'm wrong - that since I have very little hands-on experience with the iPad I'm hopelessly uninformed - and that I
can have all of the above right now, I'd be beholden to you, and I'd be on my way to the Apple store tomorrow morning. But I'm not holding my breath.