Don't expect much
DOA: Code Chronus
It'll be for Xbox 2, I think...Code Chronus is something like DOA:Zero. It tells the stories before DOA. You have seen the opening movie to DOA:U with the young girls. Code Chronus ties into that.
And after DOA4 & Ninja Gaiden 2
Hmm..what could it be? Maybe a game for kids this time
Dead or Alive 4
As I thought, If you don't know there are two stories in DOA, the Ninjas and DOATEC (they are the reason for Ein--when Hayate can't remember a thing in DOA2, and Ayane's father in DOA3 they have changed him into Evil)...DOA4 is considered DOATEC. Which is the company in Dead or Alive. It will tell the other side of DOA, the opposite of the ninjas.
The title for Dead or Alive was inspired from the situation Tecmo was in during the development of the game.
Everything was riding on DOA..that's why the title is called Dead or Alive, because if the game failed it meant the death of Tecmo.
Like Final Fantasy for Square
If you want to know the history of DOA games go here :
http://xbox.ign.com/articles/535/535283p1.html
It seems that every 2 years there's a new DOA game