What you might consider as a content update might not be what we intend it to be. After adding thousands of new sprites to the existing package we'll have to make the decision to keep updating (and slowly go bankrupt) or close off the package and continue with a new one – I'm sure you understand.
I'm not sure what you're missing from Kenney Studio but all features are in there, there's not a single feature that still has to be added or is missing. For the price at which Kenney Studio was sold, we feel like it was a solid piece of software. We've already informed everyone who purchased Kenney Studio that they'll receive a final update and a discount for Asset Forge (absolutely not an update of Kenney Studio, as it's a totally different application).
While a previous version of Kenney Studio did mention those features, they are not planned to be added anymore as we decided to stick to the main mechanic.
Hope these answers will help, cheers!