As this story points out, most of these cases have little chance of success. If you can't show harm from the breach, you don't have a case. Just because you were exposed to potential harm by shopping at Target doesn't mean you have standing.
On the other hand, we don't know yet how many millions of customers will be harmed that haven't yet. Banks on the other hand, could argue they were harmed. As the story points out, there were costs involved with reissuing credit cards.