Inno will continue to run events and continue to add new features to the game, each of which will provide an opportunity for players to spend diamonds to buy additional event buildings, speed their progress, or buy their way out of self-created problems.I think, yeah, they are always going to be figuring out a way to get you to spend diamonds, but I understand it.
There is nothing in the game that doesn't give you the option to spend diamonds. There is also nothing in the game that requires you to spend diamonds other than the diamond expansions and the diamonds needed for those can be easily earned for free.
Every diamond transaction in the game is a voluntary transaction initiated and consummated by the player and the player alone. Inno merely exploits inherent flaws in human behavior. I can't fault them for being good at what they do.