It looks like the Okami announcement teased to fans last week is not for an upcoming sequel. According to a tweet by the official Okami account, it was explicitly stated that it will not be a sequel. The announcement, though, is still set to be published this week.
Capcom Corporate Officer and Senior Vice President Christian Svensson responded to the sequel chatter on the Capcom Unity boards saying that the announcement is to be for Japan only:
Whatever it is, it’s likely only in Japan… I’ve got no details on what they were referring to (but as has been stated, whatever it is, it’s not a game).