Blizzard has sent out mail that is hinting at a major announcement, possibly the next expansion for the popular digital trading card game Hearthstone, on July 22.

"Champions are gathering from around the world to witness the next exciting thing Hearthstone has in store. News travels far and wide in search of brave new faces ready to answer the call to arms - Are you one of them?" part of the message reads.

According to video game news website PCGamer, the last time that such a message was released by Blizzard, it contained a blueprint of the Demolisher designed to be a hint for the then upcoming expansion Goblins vs Gnomes.

With the release of Hearthstone's content alternating between new adventure modes and expansion sets, and with the previous release being the Blackrock Mountain mode, it should be safe to assume that the announcement on July 22 will be for a new big card expansion.

The theme of the next expansion has not yet been revealed, though there have been clues left behind in the message that Blizzard sent out. The trumpet sounds played upon opening the tube that contained the message gives a distinct tournament feel, and certain gamers have pointed out that the music is similar to the one that plays during the Argent Tournament, which is an event in the expansion Wrath of the Lich King of World of Warcraft. As such, along with how the message is worded, the Argent Tournament is a possible theme for the new expansion.

Other possible themes for the new Hearthstone expansion include Pirates vs Ninjas and Taurens vs Worgens.

The upcoming announcement for a new expansion comes just after a new mode for Hearthstone is released. Named Tavern Brawl, the mode is unlocked once players reach level 20 on any hero.

In Tavern Brawl, a different kind of game is presented to players every week, with gamers fighting head to head with a unique set of rules differently per week.

In a blog post, Blizzard explained that Tavern Brawl could feature preset decks, players crafting new decks based on specific guidelines and games where specific types of minions have bonuses, among other things that can happen in Tavern Brawl.