From the character descriptions, it seems likely that we can expect a lot of dark suburban drama and messy marriage stuff with a big helping of obsession and, again, all of the murder.
Caroline Kepnes, the author of the books the series is based on, actually has a third installment of Joe's story coming out in April 2021 called You Love Me, and while Season 3 won't necessarily be based on it, there are some similarities that might provide hints of what's to come, judging from the blurb:
Joe Goldberg is back. And he's going to start a family — even if it kills him.
Joe Goldberg is done with cities, done with the muck and the posers, done with Love. Now, he's saying hello to nature, to simple pleasures on a cozy island in the Pacific Northwest. For the first time in a long time, he can just breathe.
He gets a job at the local library — he does know a thing or two about books — and that's where he meets her: Mary Kaye DiMarco. Librarian. Joe won't meddle, he will not obsess. He'll win her the old fashioned way... by providing a shoulder to cry on, a helping hand. Over time, they'll both heal their wounds and begin their happily ever after in this sleepy town.
The trouble is... Mary Kaye already has a life. She's a mother. She's a friend. She's... busy.
True love can only triumph if both people are willing to make room for the real thing. Joe cleared his decks. He's ready. And hopefully, with his encouragement and undying support, Mary Kaye will do the right thing and make room for him.