Only thing I do know is Ono posted a message at one point during captivate that was
"So we're having Captivate at Rome just now! Fighting team had presentation for new future"
...So at least we know something fighting game related will be mentioned. My bet is its a 12 character trailer for vita sfxt or Darkstalkers finally getting a teaser. What I'm hoping for is absolutely anything related to the anniversary of Street Fighter and Megaman in game form somehow.
EDIT:
Been hunting the internet for leaks. Only thing I can find is Joystiq saying Inafune let something slip last month about working on something Vita during an interview so I'm betting some of that is at captivate. The biggest thing I found is some Italian staff member at Captivate posted this thing.
And another journalist tweeted that they just photographed a soldier. Found this all posted on "thesilentchief" so I have no clue about credibility. If I find any other rumors or potential leaks online as I play detective on this event I'll post em.