They've been working on it for years. The problem is how to do it where she doesn't look hokey. A beautiful woman running around in a tiny outfit beating up people with a golden lasso while wearing a tiara sounds pretty stupid on the surface. When it gets done, I bet they change a lot of things.
In that Captain America is now being done in live action (again), Wonder Woman won't have quite the same mountain of hokiness to conquer after that's released.
Captain America doesn't have a woman's body to complicate things. Anything that shows a hint of skin will make her look like a stripper.