They have to make up for the millions they wasted on this game some how. And with the falling player base (pretty much proven by bungvisions lack of a current player based stat since release) their hope is the loss of a few "vets" will be made up for with the new players.
They are already profitable. They wont release the actual sales numbers. But Destiny Sales across all platforms are over 1 Billion. Their budget for Destiny for 10 years was 500 mil. They already covered their 10 year budget in the first game. What do you think? All the DLC now is just pure profit.
Also you know that with all the Twitch/Youtube and Gaming News giving them free advertising they have huge stream of new customers. They don't need a very large player base to make a profit, as they are already swimming in loot.