We don't have any official details from Quorn yet, only that they're "working on it", and that the egg will be replaced with potato starch. However a "worldwide shortage of potato starch" is slowing down their progress.
Thank you to the change.org petition started by Tracey Dixon that attracted almost 3,000 signatures and to the Vegan Lifestyle Association for communicating with Quorn to get this information.
More: Quorn to go COMPLETELY VEGAN across their ENTIRE range of products! (24. March 2016)