this falls in line with the idea that computers of tomorrow might be what a keyboard is to a computer today.

any individual computer will be just a tool used to connect to your online virtual desktop.

can this already be done with windows virtual machine?

Sure, but I think there's more to it than that-- if you take the promise "ubiquitous computing" seriously, there's a lot of potential input/output devices available besides a traditional keyboard/mouse/monitor.