File this one under "announcement of an announcement," but it looks like Blizzard is preparing for the next big step forward for Hearthstone. An event is currently slotted for March 9, in which select VIPs and media will be given a chance to check out what's next for Blizzard's card game.
No other details are available at this time, but it should be noted that this will fall right into the window for the debut of Standard mode. The initial announcement also pointed to an unspecified Spring 2016 expansion and unless there's another surprise incoming, that should be what this is pointing to. Given the relatively quick turnaround on League of Explorers between announcement and release, a release date shouldn't come long after that.
Hearthstone may see several differences between now and that March 9 date, given some of the changes that are looming. Lead designer Ben Brode went into a few of these potential changes during our interview with him earlier this week.