I originally felt as you do, and I still don't like the expression "soft confirm" but after some thought I look at it like this. There's a voice in the trailer, it undoubtedly belongs to a character in the game. It does not appear to belong to any one else already confirmed. Ergo, it points to Ra's inclusion. Similarly, there is a "Cold Gun" looking object in the trailer labelled with the name Captain Cold. It appears in a series of objects that belong to other characters in the game. Ergo, It points to Captain Cold's inclusion. That, for what its worth, is a soft confirm.That's the whole point. You guys say "oh you're just assuming WoWo will be in" and then turn around and put Ra's on the list. Kinda hard to acknowledge your side of the argument when it's full of contradictions.
The evidence presented for WW or really anyone else are based on evidence presented outside of the scope of anything official. Thus they should be (at this stage) considered less than even soft-confirmed.