I've gotten in what I believe to be the last revision of the boards before the final.
Cartridges are completely done, so now I'm waiting on the final version of the Cards which will have the built-in power supply storage system.
Along with that, I've completed both a Pong clone and a Snake clone for the system and tested them on my prototype. You can see the code for the games as well as some documentation on programming the cartridges at the Github site.
When I get the final board revisions in, the project will be complete!