Eh, I dunno. I think Steam Machines will, eventually, win out over consoles, but I don't see it happening for a few years, at the very least. Valve is playing a long game here - I don't see them making much headway until Year 2 or Year 3 at the earliest.
I don't think the PS4/Xbox One will sell as well as most people expect them to, though. There is a lot of enthusiasm for the systems on gaming forums, but no-one else seems to care. People seem to be too busy salivating over the latest iPhone/iPad/Samsung Galaxy Whatever/etc. to care about the new consoles. I get the feeling that people will choose a new smartphone/tablet over a console when faced with the choice, which is going to massively hamper sales.
Of course, I could be wrong on that one. It's gonna be fun to see what sales are like this time next year, though!