Assuming the breach is as extensive as the article says, the likelyhood of finding any sort of suspicious activity this early after the breach would probably be minimal. Think about the number of transactions that take place every minute across the nation, and where your 1 or 2 account's (or however many accounts you may have used) worth of transactions fit in. I imagine whoever breached their system would hold on to the card information until this story peaks and then becomes forgotten.
"Check your statements for suspicious activity," isn't the advice I would give in this case...If one made a purchase at a Target store between 11/29/13-12/15/13 with the use of a Debit/Credit card, it'd be in that individual's best interest to request a new card and account number for that Debit/Credit account. This is very inconvenient, if you're like me, because I have utilized one of the cards that I made a purchase with, at Target on Black Friday, for many years. Simply thinking about the amount of time I'll have to invest in updating accounts that utilize that card makes my head spin.
However, it's a "better safe than sorry" situation that I'll have to deal with. I'm willing to bet a majority of individuals that come across the story will do one of two things:
1) Blow it off and assume nothing could happen to their money.
2) Take a second to look over their statements, find nothing wrong, and keep their current Cards/Account Numbers.
Meanwhile, this story comes and goes, and 6 months from now, a rash of fraudulent transactions take place and suddenly hundreds or thousands of individuals are now stuck with an identity theft problem, which could've all been avoided by taking the precautionary measure of having your Card/Account Numbers changed to begin with.
Just my ฿฿