Since the final DLC for The Last of Us has already came out, it leads us to believe that the secret may be related to the Uncharted series but then again, it was posted on a TLOU blog so it could mean it may be for that game, or maybe even both games!
Jason Paul states:
"I'm just surprised no one has yet to find some of the secrets we have dropped around the internet..."
No other information was given on where to find the secrets. Looks like this is going to be a long hunt.
What are you hoping for the secret to be? Comment below.