It may very well happen. The GDC website has this to say about his speech:
"In the Nintendo keynote, entitled "The Heart of a Gamer," Iwata will assess where the games business stands today, predict how it will develop over the next several years, and the manner in which it will help decide future Nintendo hardware and software development."
Sounds like the perfect opportunity to announce a plan for the DS' future. Thursday at 10:30am Pacific/1:30pm Eastern... start looking for news around 2pm. We'll be on the lookout, that's for sure.
silks