Verified answer

...... when will Ultimate Marvel vs Capcom 4 come out.

God! that Irked me. Just as I had gotten pretty high up on MvC3 leaderboards *BAMM* they announce UMvC3 coming out a few months later.

So yeah my faith in the series is a little waining at the moment.

*Tantrum over*

But to answer the question:

According to Event Hubs, there isn't any actual plans in the works for MvC4, at least not for any time soon.

http://www.eventhubs.com/news/2012/oct/19/next-mar...

EDIT:

Screwattack's "12 New Characters" is a wish list, not actual game info.

http://www.screwattack.com/news/12-new-capcom-char...

You'll have to see, there are no confirmations yet so we don't know

They are and they will supposedly add in twelve characters.