NOTE: This is not a list of features that weren't implemented, this is a list of upcoming features.
The scrapped Meteor Slimes might still be added in a future update, but this is still uncertain.
Currently none. Though it is reasonable to believe that there will be toys for each of the new slimes.
More Zone Sections/Sub Areas
Current zones will get more sections added to them and there will be more sub-areas for you to explore in the future.
More Treasure Pods
More treasure pods are planned to be added in the future updates.
Adorable Drones will be added, allowing you to automate parts of your ranching experience. Manual ranching will be still required, but drones will reduce your workload and leave you more time to explore. They will be added in The Automatic Update (1.3.0)
This mysterious gadget might be added in a future version since it's referenced in the code. It was originally supposed to be unlocked a week after you got the Hydro Turret. It looks like a ball on a stick and it has to be triggered manually (with a cooldown of 60 seconds after that). Once it's triggered, the Hydro Shower will trigger a rain effect and kill Tarr in its radius, which is about the size of an expanded rad aura.
Iron Rancher Mode
This mode adds a replayable survival-like experience to the game. It has you race against time to collect quotas of various plorts across multi-day rounds. Each round will also include mixed rules and various challenges, including vampiric chickens, random plorts, random tarr spawns, increased hunger, and more. This will be added with Viktor's Experimental Update (1.4.0).
Viktor will eventually offer you a daily mission as work-for-hire in new zones across the world. These missions will offer unique rewards as you earn them.
Viktor will ask you to perform experiments in a virtual environment. (1.4.0)
It hasn't been yet confirmed whether BOb or Thora will receive a new zone.
Similar to the Wiggly Wonderland event, a rotating stock of weekly rewards will be offered to ranchers who know how to hunt down those hidden crates across the range.
More achievements are set to be released in late 2018.