It's not necessarily like that though. I'm not talking your typical PC setup with a keyboard and mouse. Internally an X-Box technically is a PC.
The point is that the move from Playstation is removing the hardware component from the equation. In theory with a browser you could play their games on a Nintendo or X-Box or an Android box. Think of it more in the sense of the development of Netflix, originally you needed a dedicated DVD player, then you could stream on a PC, now with a cheap device like a Chromecast you can select from your phone while sat on the sofa.
I am speculating, I can't see the end game but can see trends, however I'm not suggesting at all that I think the future will be a PC setup. More that it will be hardware agnostic and delivered online.