This tease was revealed on the official Hearthstone Twitter account and was similarly blogged on the Hearthstone website. Unfortunately it is unclear as to what we might be able to expect from this, but judging from Blizzard’s past releases, Gadgetzan will most probably be an expansion since One Night in Karazhan was considered an “adventure”.
In case you’re wondering what are the differences, adventures consist of various “wings” that players can battle through to get to the bosses and win some rare and powerful cards. For the most part adventures can be soloed meaning that there is content for players who don’t mind playing by themselves.
Expansions on the other hand focus more on introducing new cards, thus giving players more cards and options to build decks with. No word on when the expansion will be announced, but with BlizzCon 2016 kicking off next week, we’re guessing that’s when Blizzard will most likely reveal the new expansion in full.