The official Heroes of the Storm Twitter account announced the news earlier this morning, likely much to the excitement of anyone who thought up a tag years ago for World of Warcraft based on their favorite song lyric at the time or a vampire OC they trolled AOL chats with (not that I'm guilty of that.)
Normally you get one free name change with every BattleTag, ever. Consider this a license to go crazy and change up your style. Just make sure you follow the naming conventions established by Blizzard here and go with something you're not going to regret later. Again. And then when you've changed your BattleTag, remember that Microsoft is doing something similar, freeing up Xbox Live gamertags that you can jump on to give yourself an online rebirth of sorts.