I just found out, that there now is a "Multi-Slice / Multi-View Rendering" entry for the Roadmap. I believe that this will enable us, to do Mixed Reality Videos and local multiplayer. I decided to tell Epic how important these features are, so they make it as easy as possible to develop these features for our games. If this is something you care about, it might be a good idea to let Epic know, that these features are very important for us VR developers.
You can also vote for "Multi-Slice / Multi-View Rendering" under the VR list in Trello.

Additional Links:
Mixed Reality Video example from Valve
more info about Mixed Reality Streaming in Fantastic Contraption