Not exactly. Remember that the Surface RT deliberately restricted the applications that could be run via Win32 on the familiar desktop. Just about every third party application needed to adopt the new RT APIs and run "Metro"-style.
If they go down this road, Apple will not put constraints like that on their Mac developers: I'd expect that all the most commonly used frameworks would continue to be available, and porting most applications would amount to a recompile against a new Xcode.
I never once gave much thought to the idea that Apple would somehow shut out unsigned apps from its desktop computers, for the main reason that there would be too many existing apps that would suddenly lose functionality and cause a backlash.
With a port to ARM, though, Apple can simply say that the developers haven't ported their app to the new architecture yet, and that more apps will become available as developers catch up. Meanwhile, all those apps that currently require some kind of lower-level access could be banned.
On the other hand, I think that would be a huge boon for non-power users; it would be nearly impossible for malware to get onto the computer, and even annoyances like Adobe's and Microsoft's auto-updaters would finally get funneled though the App Store, which would prevent programs like that from constantly occupying memory/CPU/network.
For this to work, though, I think Apple would be wise to include some kind of developer mode feature (perhaps even forking over the $99/year fee) that would allow unsigned or potentially dangerous apps to run.
All of this (admittedly wild; sorry, coffee is kicking in) speculation definitely has me excited for the future of Apple, though! I haven't felt like that since Steve was around.
"All of this (admittedly wild; sorry, coffee is kicking in) speculation definitely has me excited for the future of Apple, though! I haven't felt like that since Steve was around."
Wacky. Your vision of shutting out unsigned apps has me looking for the exits. I've been an Apple user since the 80s and I'm pretty sure this would finally make me jump ship. Apple's current Big Brother trajectory frightens me to no end.
I'm pretty sure this won't change your mind, but my view is more-or-less "better the devil I know." Trading in Microsoft and Adobe's phone-homers for Apple's is fine in my book.
I don't use Microsoft or Adobe software as it stands. Getting rid of a couple of third-party updaters I don't even use in exchange for giving Apple complete control over whether or not I'm allowed to run something is an awful tradeoff. It's just barely tolerable on iOS because I use those devices more as appliances than computers, but it's not workable for me on a real computer.
If they go down this road, Apple will not put constraints like that on their Mac developers: I'd expect that all the most commonly used frameworks would continue to be available, and porting most applications would amount to a recompile against a new Xcode.