There are a couple of new quests in Kingsmouth and on Solomon Island in general, but SWL really runs players on rails for the first few hours. It’s only after you kind of bust out a bit in Kingsmouth and on the coast that you start to find some of the stuff added post-launch.
In fact, I just remembered that the first major expansion to the game is a long quest line that starts in Blue Mountain on Kingsmouth.