Uh, what? No. The whois is a dead giveaway that it is indeed not registered to Blizzard.
Yes, this is probably fake. But I'm not sure what everyone is trying to show with the domain whois? GoDaddy is a popular registrar in the US, and DomainsByProxy is a service provided by GoDaddy to "hide" your registrar information. It's simply a placeholder for privacy reasons that anyone can order. If Blizzard were to buy a domain and they don't want to disclose it yet, they might use this service. And once the game is officially confirmed they could update the registrar data (or simply cancel the proxy contract which has to be renewed every year anyways). But citing the GoDaddy entry 3 times doesn't prove anything, just look at the official Diablo3.com entry which looks the same (except for no proxy data as there's no reason to hide anything).
A giveaway for fake though is the source code of the website. Super minimal HTML code, inline CSS, and doesn't look like any HTML code I've ever seen on a Blizzard website. The only instance I can remember seeing such sloppy/minimal website source code from Blizzard is when they hid hints to future release in the source code (as they did for the hidden lost numbers in the splash screen code that led to a hint at the D3 announcement). It also doesn't make sense to hide anything (domain owner, image, or some HTML code puzzle) if the very domain name already reveals everything...
So yeah, probably fake, but not because of the whois, but rather because of the website and its code.