So, will Shore to Sea be part of the Module SUbscription?
Yes... unique origin aside, it's a regular Pathfinder Module.
Will this be added/adapted for use in the pathfinder society organized play?
I really enjoyed the Living Greyhawk adaptable modules Wizards did before the end of 3.5 and since I only played organized play I wouldn't have bought them if they hadn't adapted them to LG.
For now, there are no rules for adapting non-Pathfinder Society scenarios to work within Pathfinder Society. Erik and I have been talking about how such a system might work, though, and I think its likely sometime in the future we might initiate a way to play modules (and perhaps even Adventure Paths) for credit in the Society. As you can imagine, it's a difficult question for us to answer right now and I have no real details that I can share.