Bruce Willis has saved the universe, identified cheaters will still be unable to play Monster Hunter 3. At least that's the case for one Japanese player, who tried to connect online and was given a dismissive prompt (in Japanese; machine translation here), indicating that he'd been banned until December 12, 9999.
The message cited "modded data" as the cause for the banning, and while we can't confirm that there was any questionable data on the system, we will say that if you're looking to hunt monsters (possibly around early 2010), you may want to avoid the uber hax!!1! option. We'd hate for you to have to go on living a lootless life for the next couple thousand years.