> It's not. The traditional method(s) will still work.
For now. I'm willing to bet any amount that in 5 years (most likely a lot sooner) this will be the only "legal" way to install software on your Mac (and you'll probably need to jailbreak your Mac to install apps through command line or something).
At which point every developer (except those working on platform-specific projects) would switch their work machine to Linux.
Phones and tablets went that way because they're new devices that weren't already entrenched in people's daily lives, and they're complementary to your primary machine. The fact that they're locked down is a dealbreaker for many, but it doesn't imply a wholesale ship-jumping like locking down a desktop would.
[Edited to clarify that I wasn't talking about the platform developers would target, but would themselves use].
I'm not sure they'll lose every developer to Linux. App Store will provide incredible exposure for their apps, which just may make it worth it for them.
For now. I'm willing to bet any amount that in 5 years (most likely a lot sooner) this will be the only "legal" way to install software on your Mac (and you'll probably need to jailbreak your Mac to install apps through command line or something).
In another 5 years or so, Windows will follow.