I'm looking at it from the point of view of the customer. If I don't have the source code, I cannot recompile the code, end of story. The company that sold the binary executable might recompile it for the new architecture, but they're probably not going to give the recompiled binary away for free. That is why I say that #3 is, for the user, only possible for open source.

I agree that vendors are not beholden to a CPU architecture, but let's not pretend that switching is immediately beneficial to the user. What you call "opening up the market", I call adding unnecessary obsolescence to programs that chose not to add planned obsolescence in the first place.

If anything, I would take this as further evidence that software should be sold as source code, because the utility of mere build artifacts can be taken away.

You can conjure up fictitious reasons, but the manufacturer never guaranteed the buyer that future hardware versions would use the same CPU.

Then there's your contrived reason to obtain source code - another bogus, non-sensical reason that'll never fly with devs.

You always have the choice of staying with an older model, or better, using Linux on your custom hardware. Don't push your socialism/communism on one of the most capitalistic companies on Earth (Apple)