We’re at least 2 years for that to be a reality.
Realtime facial tracking currently lacks proper cameras ( no 60fps to be seen around so goodbye proper lipsync, unless you use a GoPro with a proper usb/hdmi converter ) and technology, even if Faceware is about to release the tech for everyone to use.
Simply put you might want to record an animation and then import into UE4, because direct input ( without any proper tweaking/smoothing and so on ) will look like ****.
Also, facial movement are way too subtle and a 2d image wont capture all the expressions…when 4D scan will be processed in realtime then we can talk about something incredible 