The Sims 4 is still months away from release, yet the community has already began development on custom content creation tools. Maxis revealed the game file format in the recent Create-A-Sim tool demo, allowing capable programmers to begin the reverse engineering process.
Prof.net has already created a CAS editing tool. Already it’s possible to create non-default recolors of clothing and other aesthetic elements.
A general purpose package editor is also in development, with source code and builds available at GitHub and discussions taking place at Simlogical.
Early reports suggest that the package format used by The Sims 4 is incredibly similar to that found in TS3. If that’s true, once the game is released it shouldn’t take very long for quality custom content to start becoming available.