Which would instantly kill the Mac as a development platform, and render all previously purchased software irrelevant. This just won't happen, though I can see a version of OS X that does this by default (perhaps on all "non-pro" models).
(The iMac may have been a few years too early - they could have positioned the iMac as the trojan horse in this story).
Remember how much business they lost last time they did this (the intel switch, or even the os x switch)? Oh wait...
I suppose if the announced that this was the plan, and gave people years to migrate across, it might be something they'd do. But it would kill basically any technical use of the platform (development, scientific computing). I find it much more likely they'll evolve iOS "up" to support users for whom a closed appliance approach is helpful, whilst adding options to OS X to cater for those who want a more traditional computer but need a bit more help.