I already said this once, it might be a possibility, but this way isn't going to reach every flashcard user, since not everybody is connected to the internet AND if it happens to a few people and they post about it on the internet, they are going to warn everybody to stay away from the internet (untill a fix is found, if their is a fix...). Also it has been a couple of weeks now that nintendo has commented that they are going to use new security to harden pirating games. If you ask me the latest solution is the best (for them) since pirated games; roms , reach the entire flashcard community. In case of the internet people are just going to stay away from the internet and still play their roms offline. And also the ds phat & lite also have internet capabilities, updating firmware and such, so why didn't they ban the last-generation flashcards then? It seems to me that it isn't as simple to ban it through the firmware...
We must not forget that nintendo wifi isn't xbox live, meaning nintendo will never be capable to reach every flashcard out their at the same time, resulting in only a small percentage of the cards being banned.