Even a 5.5 inch iPhone would be closer in aspect ratio and size to a 16:9 4 inch iPhone than it would be to a 4:3 7.9 inch iPad Mini (let alone a full-size iPad). to me, that makes it obvious it would run scaled-up iPhone apps, not scaled-down iPad apps. In other words, a larger iPhone will clearly be on the "phone" side of the phone/tablet line.

If you want to argue that it is all a continuum and that the scope of touch-based computing hasn't changed, I'd agree with that. But in a thread that started by talking about iPhones, iPads and Windows 8, "tablet computing" is more specific than that.