There is actually one application that will delay, if not stop, the extinction of the PCs in the enterprise world: Excel.
Excel is by far the world's most popular business intelligence tool. Also, it is probably the world's most popular project management tool. In Japan (where I've done some business in), it also serves as everything from billing software to a mockup tool for digital products.
You might say that Macs have Excel too, but any business analyst types worth their salt know that the two Excels are vastly different.
Case in point: the very graph that shows the rise of Macs (quoted in the article and credited to IDC) seems to have been produced in Excel on Windows =)