If you load up your post-completion autosave, you are placed back in Hawke's estate and get a message thanking you for playing the game and that you can use your writing desk to accept any future DLC missions, so yes it seems more is on the way. There's
been no announcements about what they are and when they'll be out that I've seen though.
On the Bioware Social Network the devs (both the lead writer and lead cinematics) have stated they're revising the story DLC to factor in the complaints like "the repetive locations, magically appearing waves, etc" so that the future story DLC will not have
the same problems people had with DA2. Thus why they're not rolling out the story DLC as quickly as they did with DA Origins.