FAKE. As stated build numbers seem off. Also I find it funny that he didn't show Siri actually working. Wow, He brought it up? I wouldn't doubt if he didn't have it even connected to a working proxy server. If he did he was more than likely nervous to show on video if the proxy server went down or didn't work.
Apple already added a dictionary into iOS. You can highlight any word and define it. I don't see Apple adding an App for it. If anything they would just integrate it into the Spotlight search and have a button on the right hand side that would bring up the dictionary. I do question some things Apple has done lately in software, but them adding an App for dictionary when it is already built into iOS? Not likely.