Not at all. What makes a gaming PC is the massive variety of hardware and software configurations; that is both a positive and a negative. You're never guaranteed a game will work OOTB or support your preferred control scheme/social gaming network on a PC as you are with a console, that's huge for an entertainment device - most non-geeks don't want to futz with drivers or tweak .ini's to resolve quirks.
OTOH, with a closed platform you're stuck with what the developer targets as an acceptable tradeoff with respect to quality and performance in games. Hate massive screen tearing or sub-30fps? Tough, that game you love will be forever marred by the decisions the developer made. A PC, adjust the settings or just throw more hardware at it down the line, and eventually you'll have the best version of cross-platform games out there - again, provided they work.
I don't necessarily think this will be a success (because the competition is tough), but it's not a new magical idea Valve is making here, it is literally a video game console.
Only if you use the popular misinterpretation of "literally" as "figuratively". They're not building the hardware, they're not locking it down. They're making a somewhat restricted platform that is still open - you'll be able to put Windows on this if you want. They're trying to bridge the divide between closed and open platforms and retain the advantages of both. In theory, of course - the real nitty gritty details are still scarce.