@Palmetto: That isn't true. My company has VoIP desk phones and VoIP soft phones (on PC's) and now has Microsoft Lync as well. Though Lync is primarily an IM service, it has the ability to make calls via our VoIP system. When at home, I can VPN into the company network, then make calls anywhere in the world. This is important as I sometimes have to support systems in India at two in the morning.

Where I think the author is mistaken is that tablets will be the replacement for the desk phone. I think it more likely that a service like Lync will front the phone system and apps like the Lync client, which is available on iOS and Android, will find its way onto user's cell phones. Most smart phones have the same internals as tablets, are easier to carry, and are actually designed to be used as a phone.