Hmm....
I am not a 100% that the Sims 4 will see no more involved gameplay added to the game.
The latest piece of involving gameplay.
The latest piece of really involving gameplay was Cottage Living, and that was very good according to me. I have gotten a lot of enjoyment out of that expansion and it did change the game for me. It could have been a great goodbye gameplay-wise or we will see something good added later.
What is happening currently.
At the moment we are getting everything that does not include gameplay. BB, CAS and now a world.
Hm.... Just because we are not seeing any involving gameplay added right now does not make it a 100% certain that it will never occur again. The people who make that kind of content are either working on something or laid off. If it is something coming out for Sims 4 or if they are involved in something else time will tell.
Could it be story progression that involves the entire world? Do they wish to add something big that will be added as free content? Are the gameplay-people working on something other than Sims 4? I don't know.
Maybe it is because I came to the Sims from other games, I am used to waiting years for the next addition to my favorite games but I feel like it is premature to write of future gameplay content completely when the latest expansion was so great. Am I certain that we will see more, no. Am I certain that we will see no more, no.