At some point phones will be good enough to run a full blown OS
They already are. My Nexus 7 tablet has about as much RAM as my netbook, and I happily run Xubuntu on my netbook.
Need a keyboard? Oh carry one of those too. Etc. Before you know it you are walking around with a suitcase of components and cables to connect them all together.
The idea is that there'd be a monitor and possibly a keyboard at each work station, and you plug your own phone into the monitor and pair the keyboard. Or if you're worried about a keylogger, all you need to bring is the keyboard. At that point, you could use anyone's HDTV as the monitor.
Desktops are just too powerful and cheap to not have one.
My fear is that once the PC becomes perceived something that people buy only to use at work, PC makers will get away with charging inflated "enterprise" prices for them. Case in point: the price of a 10" laptop rose sharply at the end of December 2012 when netbooks were discontinued in favor of far more expensive x86 tablets.
I'll pay 500-1000 for a faster device and saving a few minutes a day for a few years and suspect most businesses will too.
That's just it: if it's something that only businesses buy, too bad for home users who have a need for one or more PC use cases.