Ryota Niitsuma, producer for Marvel vs Capcom 3, has confirmed that they will be unveiling new characters for the game around Tokyo Game Show. He made the reveal in the latest post on the MVC3 development blog. According to Andriasang, he said he is working on preparing for the show including setting up the new character reveals and getting some special guests for a Marvel vs Capcom 3 stage show. In the post, he mentioned that announcements may be made before the actual show begins, possibly when we least expect it.
Tokyo Game Show begins on September 16th and runs for three days, with the first two days being for press and business and the last day being open to the public.