Greetings.

I've followed the whole 7th Umbral Era storyline and documented it in my Journal, so I've almost certain proof of what the “Survivor Mark” is going to look like and where it'll be placed.
If you read all the dialogues in the Grand Company Quests, Cid and Louisoix gave away huge hints about it, but if you didn't pay attention or just skipped everything, here's a preview (obviously it'll be available only to those who participated in the 7th Umbral Era):