As far as they said in several of their streams on Twitch, they will continue making DLC so long as people keep asking for, and buying them. They like when people play their games, and give them ideas.
Also benefits of DLC is they open up more of their engine to modders. I also like the Cloud Saving, I've lost my saves a few times.
They never actually said the last one was to "be the last". In fact they said they have several more planned through next year.
I saw the livestream. The guy they interviewed there stated that the Old Golds was the last DLC released for this game.