There’s a lot of speculation about what the green vortex could be: a portal to another world, a portal to our world, a portal to FTL, a portal to Oz. So, I’ll add my guess and say it’s a portal to Neverland.
Also
You see how in the end Emma kills something well you know how in the show they say if you kill someone you become just as evil. In this commercial it looks like she kills Regina?? what does this mean?
Either that scene is Regina’s nightmare, or it is real. If it is a real event, then I don’t think Emma would kill Regina, since presumably Snow White and Prince Charming would warn their daughter not to tarnish her soul and become as dark as the one she kills. Perhaps Emma is just swinging her sword in Regina’s direction but comes short, just to scare Regina. Perhaps Emma uses the sword to slice off a branch from the apple tree, which would be similar to a scene in episode 2 when Emma uses a chain saw to prune the apple tree. There is some special link between Regina and the apple tree. Back in episode 2, Regina made a speech about how the honey comb apple tree can survive any storm, which is why I think the apple tree is a metaphor for the tree itself. Perhaps if you harm the apple tree, you also harm Regina, (but without all the horrible repercussions of killing Regina directly).
"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy