I can't disagree with your information about performance of tablets versus some other form factor. However, you haven't addressed something I find more compelling as I get older and my eyesite isn't what it one was - display size.
As an example, I recently decided to replace my failing Nook HD+ 10" tablet with something else. I wasn't interested in going smaller after enjoying the 10" display size and resolution of the Nook. I was looking for a tablet I could use as a reader (in portrait mode). What I discovered is that most tablets use screens with the aspect ratio of 16:9 or 16:10 meaning that when you use them in portrait mode, the screens are long and narrow. If you're viewing a magazine on a 10" screen with a 16:9 aspect ration, the page is scaled to the display width reducing the page size to about what it would be on a 7 or 8" tablet. My Nook didn't have this issue because the ratio was 3:2 which is a nice comfortable page size for reading which approximates that of a physical book. Here's a comparison of different aspect ratios. My options came down to a small number of tablets where there wasn't some trade-off I was forced into.
My point here is that since that majority of tablets and mobile devices are in the 8" range, they're limited in use due to the size of the display. While we could run pretty much any app in a web browser on such a device, I don't see that one could effectively use Photoshop on devices of this size. I see tablets as interim devices. Good enough for when using a full size device isn't a practical option. As such, I don't really see them entirely replacing full size devices.