I think it's safe to say that even beyond Wasteland Workshop there will be more settlement stuff coming down the pike. I'd also be surprised if building systems don't become a staple in all Bethesda games from here on out, given Howard's comments quoted in http://www.ign.com/articles/2016/03/17/fallout-4-director-workshop-popularity-was-the-biggest-surprise-for-bethesda article.
Personally, I'm okay with that. I've had a lot of fun with the settlement system.
Also, the comment about how much content is in Far Harbor is worth noting. More than Dawnguard, less than Shivering Isles. I remember the main quest of Shivering Isles, but I'm having a hard time remembering how much side content there was.