No, it doesn't mean that your dice will only roll 5s and 6s for the entire year. It means you get free stuff. A lot of free stuff. Games Workshop is giving away one of every release they have (well, almost every release) for an entire year to two lucky winners.
From the announcement:
You read that headline right. In 2022, we’re offering two lucky people the chance to win one of every plastic Games Workshop model kit, every Warhammer 40,000 and Warhammer Age of Sigmar supplement, and every Black Library novel that we release during the year. Every box. Every miniature. Every book.*
That’s a pretty sweet prize.
Entering couldn’t be simpler – every £10 spent on the Games Workshop webstore between now and 11:59 pm GMT on Saturday the 1st of January grants you one entry, and you can enter as many times as you want.**