They might have no plans at all in this area. They might have plans to work on this invention soon, or some day. They might have it working in the R&D lab. Or they might have Macs with this feature already on trucks, ready to arrive at Apple Stores, and be poised to announce them tomorrow. All we know is that Apple has a patent in the area, which sparked our speculation.
The idea seems basically simple. LEDs around the outside of the Mac allow programmable color in the enclosure. It could be limited to one color at a time for reasons of technology or economics, but we can't rule out the possibility of cases with "addressable" LEDs so that different areas, or even different pixels, could be controlled by the computer.
The ideas for practical use of such a feature are limited only by our imaginations. For starters, you could set it to your favorite color instead of making a permanent choice of color at time of purchase. Your case color could be varied to suit your mood. Your entire Mac could blink to tell you that a dialog box is waiting for you to click something. Your Mac could be used as a traffic signal. Your Mac could play that "Simon Says" game by changing colors in a pattern and asking you to replay the sequence. Your Mac could display your favorite photo on the outside of the enclosure. Your Mac could change colors in time to the music you are playing. Your Mac could use a camera to detect the color around it and try to blend in!