Given that the last one was pretty soft, I think it is unlikely that the next one will come from a ballad (though it might...). Personally, I think it will be Lost Not Forgotten, though I'm hoping for Outcry.
By the way, maybe the early release of the last snippet (on a Wednesday and not a Friday) means that they will release a snippet from each song. If you take out On the Backs of Angels there are 8 songs left, 2 of which had already been teased, but only 4 more Fridays until the release of the album. Then again, this might be a one time event, given that Far From Heaven is really pretty short and we have enough Fridays now for the rest of the songs.