There is chance that a lot of figures have already been produced but those might not every be shown. Here is the statement from Mattel about the canceling:
Unfortunately, as you’ve probably noticed at Target, Young Justice didn’t work out well at retail and will be going away. We’re disappointed, but that’s how it can turn out. That doesn’t mean you might not see more one day on Matty.Mattel has suggested the action figure line could possibly continue through their adult collector website Matty Collector. No confirmation has been stated if the rest of the action figures will be available through Matty Collector.