This happened to me once with Citibank before as well.

This situation is more likely related to the Heartland hacking incident that was recently reported. Something like 100 million cards at any of thousands of merchants. We had several (non-Citi) corporate cards canceled last week during a company meeting. My bank also sent me an email to tell me a new debit card is on the way.

As far as I know most companies are sending the new cards before canceling the old ones as there are just too many to cancel (take the financial system to a halt!).