IIRC they no longer have keynotes, and that one was the last one.
While no major keynote will take place, several track keynotes are scheduled:
Audio Track: "Build That Wall: Creating the Audio for Bastion," Darren Korb, Audio Director, Supergiant Games
Business, Marketing & Management Track: "Why 'Free' and Cross-Platform Is The Future of Gaming," John Schappert, Chief Operating Officer, Zynga
Game Design Track: "How I Got My Mom to Play Through Plants Vs. Zombies," George Fan, Senior Game Designer, PopCap
Production Track: "Concrete Practices to be a Better Leader: Framing & Intention," Brian Sharp, Lead Engineer, Bungie
Programming Track: "Designing a Technology Strategy for a Large Publisher," Julian Merceron, Worldwide Technology Director, Square Enix
Visual Arts Track: "The Art of Diablo 3," Christian Lichtner, Art Director, Blizzard Entertainment
Source:
http://www.gdconf.com/news/gdc_2012_adds_track_keynotes_f.html
Epic Games hosts seven sessions:
Production Culture: How Two and a Half Artists Completed the FX for Gears of War 3
Wednesday 11:00AM
Francois Antoine (Epic Games, Inc.)
Gears of War 3: Building a Better Pipeline (Presented by Autodesk)
Wednesday 3:30PM
Jeremy Ernst (Epic Games)
Bringing AAA Graphics to Mobile Platforms
Thursday 10:00AM
Niklas Smedberg (Epic Games)
Tackling Large Scale Destruction FX: Lessons Learned From Raam's Shadow DLC
Thursday 12:05PM
Francois Antoine (Epic Games, Inc.)
Evolution of the Cinematic Process: The Gears of War Trilogy
Thursday 5:30PM
Greg Mitchell (Epic Games)
Re-orienting Development and Accelerating Production to Create Infinity Blade and Infinity B...
Thursday 5:30PM
Simon Hurley (Epic Games, Inc.)
Gameplay Data Analysis: Asking the Right Questions
Friday 10:00AM
Ian Thomas (Epic Games)
Out of these, I'd say the last listed is the one most likely for this Unreal Engine demo to appear on. However, that's on closing day and not probably the premiere venue for this, so could it be that Epic Games will throw a press conference first day to build interest early? In other cases they've got a big booth (40' x 70') in the business center and could certainly demonstrate the new engine stuff there:
Full floorplans here:
http://www.gdconf.com/pdf/floorplans/GDC_2012_FloorPlan_02_24_2012.pdf