In systems theory we call this "boundary spanning" - when one system overlaps another. By that I mean traditional notions of telephone or of Internet overlapping to create a region where something new exists. A model of Skype as a phone service must include a fixed device like a computer or game console. A model of Internet communication includes both fixed AND mobile devices. So we really need to look into Microsoft's crystal ball to fully understand where Skype is going. Of course MS sees a future in fixed communication, but just how it will look in 5-10 years is still a mystery to this technology pro.
Microsoft at Work on Meshing Its Products With Skype - NYTimes.com