It had been rumoured that a number of community members and top pros had been invited to Blizzard last September to discuss the future of Hearthstone, and that it was there that the idea of formats had first been presented outside of the company. Now we have confirmation as not only did Trump and Kibler, along with a dozen or so other pros, head along, but Polygon were invited as well to document it, with their story being published today.
Here's the best Hearthstone decks for beginners, which we'll be massively updating once rotations begin.
It turns out that the originally proposed version of the system was familiar to what we see now, but a little more limited in scope, only binning a few sets. Originally to be announced before Blizzcon, it was pushed back to this year so it could be iterated on some more, at the suggestions of those community members.
Turns out that even the bits that did make it through which people aren't hot on were discussed. Brian Kibler, particularly, was a fierce detractor of the idea of leaving the Classic set in for all-time, as I was too when I first heard about it, believing that it would lead to too much sameyness in deck design between standard formats. He and others also weren't a fan of taking the single-player content off sale once it rotated out, seeing it as a great thing for new players to try even if they couldn't use the cards.
Blizzard's reasoning for the latter, at least at the time, was not only to stop players buying something they couldn't use, but so that they could have a 'coming out of the vault' moment for their old adventures when necessary. A special event where they would be buyable and playable for all.
The full article is well worth a read if you're into Hearthstone. Note that any changes to the system mentioned there are from before it was announced - anything that contradicts that announcement shouldn't be taken as gospel, and doubtless Blizzard will pop up soon to right and wrongs. There are more recent comments on the changes between what they saw at the summit and the final version from players too.