Just received an email at work, the content, was a notification to all holders of US licensed aircraft mechanics, pilots and repairman's certificates .
On March 31, 2013, all holders of these licenses that have not yet replaced their paper licenses with a plastic copy, will not be able to exercise the privileges of that license .
So pretty much, if you don't replace your license by then and get caught afterwards, you're in violation of FAR Part 65.15 and can receive a violation on your license .