Which part of the video do you mean specifically? Some of those content examples have made it into separate projects. For instance the butterfly is in the Blueprint Office map. The ice, fire and metal spheres are in the Content Examples project, if I remember correctly. It seems like they just split them up into different projects.
Maybe some of them were not quite ready yet. Or they used some “hacks” that relied on private engine functions.
If you meant the cinematics in the first part of the video, that’s an other question. We already got the Elementals demo. So maybe, we’ll see this one too, one day. About the Elemental demo, Epic said, that the videos that were showcased early on, were done in an earlier version if the engine and it took some time for them to update the project for the current version. That could be a reason too.