If you aren't referring to the ones from quests, like Ace of Spades, Tlaloc, and Fabian Strategy, then a lot of people are getting them from engrams dropped when they use 3 of Coins. That's how I've received most of mine.

I've only received one of the new exotics. The Hereafter sniper. I haven't had the time to play lately but if you finish the Petra and Variks questline and you are rank 3 with Petra, you are guaranteed to get Boolean Gemini the exotic scout rifle.