The following is an introduction of data released as leak information. I found the data using hearthstonejson.com
According to the comments by Mike Donais, it seems the leaks are confirmed. Also, it seems that perhaps the 4 new heroes will swap with other, too powerful heroes to balance the meta.
Sir Finley Mrrgglton
Hero Power
Activ Hero Power: 1 Gold
Effect: Give a random friendly minion +1/+1. After you sell a minion, refresh this.
Elise Starseeker
Hero Power
Passiv Hero Power
Effect: When you upgrade Bob’s Tavern get a ‘Recruitment Map’
Recruitment Map: Discover a minion from Tavern Tier 0. (I guess the 0 is just a filler and will be updated based on your Tavern Tier)
Brann Bronzebeard
Hero Power
Passive Hero Power
Effect: After you play a Battlecry minion, give a random friendly minion +1/+1.
Sindragosa
Hero Power
Passive Hero Power
Effect: At the end of your turn, Frozen minions get +1/+1.