It sounds like Phoenix Wright (Ace Attorney) and Ingrid (Capcom Fighting Evolution) are the most likely candidates, but there's still some hoops to jump through as Nintendo has to sign off on the whole thing and of course Capcom would have to actually do the work.
If this comes to pass, it would be a big change of pace for Capcom, as they've stated multiple times they wouldn't add characters via DLC to Street Fighter IV as it may upset the balance of the title, although it sounds like they're not as concerned with a Vs. title.
A lot of speculation here still, and there's been no mention of who might be coming in on the Tatsunoko side if this comes to pass, but possibly something to look out for.
On an unrelated note, these two new gameplay videos were added to Capcom's press site, check them out.
