The lines will blur anyway. A Microsoft Surface combined with a TypeCover (assuming it works well), could be used as both a tablet and a laptop at different times. Does it then contribute to PC sales or tablet sales?
Form factor is generally insignificant; there's a big difference between a laptop or a workstation but you would still call them both PCs, even though the working patterns with each are quite different.
The important difference is 'internet/media consumption device' (iPad) vs. 'general computing and productivity device' (PC, Surface?). I believe the growth and shrinkage of their respective markets indicate the typical consumer's desires.
Blurring is what Microsoft hopes to happen. But I don't see any evidence that this hope will be satisfied. It's like crossing a camel with an ostrich and hoping it can fly.
Microsoft failed in previous tablet efforts by trying to graft the desktop environment onto a touchscreen. Failed miserably, and not because of hardware immaturity. In contrast, Apple has succeeded immensely by discarding the desktop metaphor and embracing the touch environment exclusively. Microsoft is trying to straddle the two environments solely to prop up Windows, not because it's a better UX. This to me, dooms it to failure, just as Microsoft failed in its previous tablet ventures.
The important difference is 'internet/media consumption device' (iPad) vs. 'general computing and productivity device' (PC, Surface?). I believe the growth and shrinkage of their respective markets indicate the typical consumer's desires.