I have a hard time understanding how anybody could expect or position any computer of any kind to be the one and only replacement for all previous computers. Maybe Google is merely claiming that netbooks with Chrome OS can replace some computers running full-fledged operating systems?
People might have owned only one computer (if any) in 1998, today it is very easy to afford many computers and computer-like devices. (You can basically buy two cheap laptops for the price of one middle of the road 1998 desktop.) Am I the only one who constantly sees some kind of laptop (the second or even third computer in the household) in all kinds of (non-techie) living rooms and kitchens? People want to be able to quickly check the weather, the news, that route, their emails and random stuff without leaving the living room.
I can’t speak for other households but for my parents their cheap living room laptop is the main computer in the household. They use it constantly to go online or read emails, the nice expensive desktop in the office gets hardly ever used.
Netbooks running Chrome OS and tablets (like the iPad) are perfectly capable of replacing those living room laptops. In that sense, sure, Chrome OS is a good candidate for replacing certain computers. The key word is certain.