Whether what you have is called a "PC" is pretty irrelevant... You'll have a monitor, a keyboard and a mouse that go somewhere. For the end user the difference is negligible. As for the desktop phone? That could happen, but it seems less likely in a "no PCs but virtual workstations" scenario because of the way that voice traffic works... If the phone is disappearing because "they'll all use mobile phones" then I'll just laugh derisively: Mobile technology isn't there to provide the same level of reliability that landlines do, and businesses crave reliable communication. Then there's also the albatross of billing and privacy on mobile platforms...

I have a hard time seeing how your desk phone could "go away" anytime soon until a large number of non-trivial issues get solved.