When the Apple watch has a SIM I'll buy one
Expect that will generate a few groans, but from my perspective, the iPhone was a game changer. Just at the point where I was sick of carrying around a phone, a music player, a diary, a notebook and who knows what else, the iPhone 3 was the only thing that looked like it could replace all those things. I got one and became an Apple convert.
I never got an ipad because it couldn't run Excel VBA. I got a MacBook Air instead. Now I've got an iPhone 6s plus because the screen is big enough to show off my photography and I'm still only carrying around 1 bit of kit.
My ideal would be to make and receive calls on my watch and carry an iPad mini. I understand the battery life on the watch isn't that great either, so that would need fixing too