While I think a hue/saturation slider would be possible for everything in the game ..... it would be a lot of work, but still possible to do in TS4, but CASt'ing abilities I don't think will ever come.
In TS3 everything was set up from the beginning to have channels which separated where/what parts something could be recolored/retextured/repatterned.
In order for a true CASt function, every single texture on every single object/door/window/wall/floor/CAS items would need to be completely redone to indicate which parts could be changed.
Even doing it the way TS2 did with certain parts of objects having the ability to pick different textures for certain parts of the items (ie: bed sheets and bed frames, countertops and counter bases, plants and plant vases/pots, etc), would be a TON of work.
So yeah, I don't see any of these scenarios ever coming to TS4.