There are rumors it might be a DOA character, so I would guess *IF* that were the case it would be Kasumi or Honoka, since they put Honoka in a crap ton of stuff. She's in Senran Kagura now and she's going to be in a Dynasty Warriors style game as well.

It says something about how disappointed I am with Tekken 7 that I don't want to see Honoka (whom I adore) in Tekken 7 because I think they will ruin her

But again this is all just speculation