The Emma holding the sword scene seems to be for this week’s episode, although the promo mentions “only 3 new episodes remain” so I’m not so sure… I’m assuming it is this week’s episode & like many others I also believe that it most be a dream/nightmare, not sure if Regina’s or Emma’s tho. What makes me think that it’s not real is that Emma is not a killer & in this scene she’s going all queen of hearts on Regina!
Update:
I re-watched this promo from last week (http://www.youtube.com/watch?v=uZYettYhcDk&feature=related) which shows scenes of all last 4 episodes and I guess that the scene maybe be for 1 of the last 2 episodes. Mostly because Regina is tied to what seems like the apple tree that comes out of nowhere which apparently is going to be in episode 21. And I still think it's a dream because this promo shows Henry among the people & I don't think Emma is going to kill someone in front of a kid… unlike Rumple.