Set top boxes may be running WebKit, but they aren’t going to need WebRTC for your living room anytime soon. The main use case of video chat with others is a hard nut to crack in the living room environment.
Google just announced their intent to make QUIC an IEFT standard. QUIC also has a role to play in WebRTC by replacing SCTP. QUIC brings with it faster connection times as well as better congestion algorithms.