Well, it's probably coming this month
As everyone knows Battlefield 4 Premium members get access to DLC two weeks early, and in their attempt to promote a 20% off sale of the service, they seemingly jumped the gun by announcing the Dragon's Teeth add-on date of July 15th by way of Twitter.
I say "jumped the gun" because the date was promptly removed and followed up by a generic "two weeks early" message. MP1st managed to capture the original tweet before it was removed. So if you're still playing Battlefield 4, expect the new DLC this month.