Don't pretty much all games have a point where you reach the 'end'? Most MMOs have characters leveling up and when you reach the top level, you're pretty much done. There might be a few top level monsters to kill in groups, but if you manage to work your way through those, that's it, or if you don't have the time to go on long raids you reach the 'end' of what you can do with your character much sooner. The point is to have content enough to entertain and occupy someone long enough that they keep paying for the subscription or decide to buy some of those extras.
Salem being a sandbox setup alters the dynamic a little bit, but it's still pretty much the same story. People will reach the 'end' eventually no matter what. They will have all the skills and all the things. The question is, will they have so much fun, that they want to do it again with a new base and new character? Will they enjoy the game the first or second time around enough to buy stuff from the store? Will there be enough things to do that making a new base might be worth the effort and expense? Right now the answer is mostly 'no', except for those few who have managed to stretch the entertainment out by messing with other people, and even that is starting to get boring.