I don't think it ever really caught on that well. I had the game back when it came out for a while, but I guess I never felt like there was enough in the way of customization options for the bots. Custom Robo has actually had a few entries in the series though, so maybe we'll see another sequel one day.
You know, I'm not even sure if Nintendo Wi-Fi Connection for the DS even still works anymore. My girlfriend was setting up her XL the other day and went to mess with the DS online setup, and it wasn't working. I think I recall some DS pokemon games losing their online connectivity recently.