Utter nonsense. How would an ARM MacBook "open up the MB to whole lot more apps"? It would in fact break all existing OS X apps, or force them to be run slowly in a virtual machine. Are you talking about iPad apps? Those are mostly designed for a touchscreen that lies flat. Even if they could be used effectively with a keyboard and mouse, the experience of switching between iPad apps and OS X ones would be, well, Microsoft-like. Try downloading Xcode for free on the app store- it comes with an iOS simulator. Try using iOS apps on your Mac for 5 minutes and you will want to die.