I don't know that I would say we should see an entirely new land every year. I would agree that they should be doing what Universal is doing, which is every year there should be at least one new Ride/Attraction. (Though a lot of the times, Universal is doing the "replace an old ride with a new one".) But an entirely new land every year forever seems overly optimistic with 2 new attractions + dining and shopping seems overly optimistic.
I honestly think expecting additional new experiences in 2020 and 2021 are pretty likely. With the 50th coming in 2021, they are going to want to be able to highlight some additional growth as well. Just anything out as far as 2020, well it's a bit early to be showing their hand. Maybe at
D23 this summer.