We're reaching out to Blizzard for comment, and we'll let you know as soon as we hear anything else.
Update: The listing has been removed from the convention center's events calendar, but it's preserved in the screenshot above. We will continue to keep an eye on the situation and will make updates as necessary.
Update 2: Blizzard responded to our inquiry about the Anaheim Convention Center listing with this: "Blizzard Entertainment has not announced any details about the next BlizzCon. We recommend that players refrain from making any BlizzCon-related travel plans at this time."