No iOS device is competition for a Windows Surface Pro. It's like saying a rowboat is competition for a freighter.
I can visit a job site and run CAD on a Surface Pro or Wacom Cintiq Comp. I can draw new designs accurately with a proper stylus. I can edit promo films in a comfortable position in the living room. I can kill 2 hours stuck at the airport getting some work done while listening to podcasts.
Or, with an iOS device, if I'm very lucky, and I've exported hundreds of duplicates of my files in just the right formats, and the companion viewer app is working, I can... view them. Wow. Super. I can crudely fingerprint some blobby streaks where my lines should be. I can try to listen to podcasts, but they won't have updated because the autoupdate never works. But I can check my email. ...which can be done quicker over a phone. I can pull up a map & see my GPS marker, but since it can't save the maps it loads, as soon as I get off the highway for gas, it dumps all the maps and I'm driving across grey squares. I can plug it into my rental car, but it won't charge.
The iPad with iOS is a nearly completely useless toy.
Apple will make the large-size hardware people want, which will be less of a mobile device and more of a productivity device, and priced as high as a decent notebook, and then cripple it by putting the iPod OS on it, so teenagers can play games on it. And they'll sell a load of them anyway.