However DoA in the past had already interacted with the Fatal Frame series, just as with Monster Rancher or Super Swing Golf; and by the way in general Tecmo has a tendency to use guests in and from their owned series, as demonstrate Rio in DoA Paradise, or the Doa/NG characters in Dinasty Warriors.
How else would you be able to milk everything from a marketing standpoint? Next year you might just see a DBZ and Yu Yu Hakusho or BleachxNaruto cross-over products (wait, have they made the initiative or not?). Imagine how much publishers.
Ehm...
(And this is just one of the first trailers, the complete game include many more characters - playable or supporting- from different series)
By the way this is a game dedicated to the most main popular characters of the Wekkly Shonen Jump (the magazine that serialize and seriazlied in Japana many manga series of success), so technically no one is a guest.