The Witcher 3's Hearts of Stone DLC is set to drop on October 13, along with a physical version that came packed with Gwent cards. Now CD Projekt Red has noted that due to logistical problems, this edition has been delayed for "several days after launch." It is currently working with GameStop to rectify the issue.
No it's not a big deal at all, but it's something to be aware of in case you don't get your shipment or pickup the day of launch. Still, people love their Gwent, so they probably want it sooner than later!