Wouldn't be tough to do. They evidently have some big things planned, DLC-wise, but they're keeping mum on it for the time being. No new races or Origins, though. A new race would also mean a new Origin, which would be way too much work for DLC. It'd require all the old voice actors to come back, have new interactions with the party, and with other people. Also, there'd be all the interactions for all other NPCs that have different interactions per Origin or race, etc.
As far as announced DLC goes, there's the Stone Prisoner (Shale) and the other stuff that comes with the Limited Collector's Edition, but that's coming out on launch day. The reason it was not included on the game disc (for both of the launch-day DLCs) was that, basically, it has to do with the lockdown of content -- the Stone Prisoner is free for everyone who pre-orders, and the Warden's Keep is free for the D2D versions of the LCE (to compensate for not getting the physical goodies the retail LCE includes).
BioWare developer Fernando Melo has indicated there are NPCs who actually sell in-game DLC for the Stone Prisoner and Warden's Keep.
This freaks me the hell out, though:
Orson Scott Card to write Dragon Age comic book for BioWare.
In the comic, will the same-sex relationships from the game be quickly followed by a punitive twenty years in the electric chair?