Not sure I understand. Both SilentCircle and Lavabit have ceased offering their services. Are they now combined in an advocacy group to design a new email protocol and get it adopted by the IETF?
IETF adoption is a red herring. The IETF does not matter. What matters is market uptake. Reputable providers will need to offer the protocol as a service, and popular client software will need to integrate it into their applications.
Silent Circle has ceased offering an email service, not all services.
IETF has become less relevant of late, they don't get stuff adopted and have been taken over largely by architecture astronauts.