If someone put the Doom3 engine to really good use (both large outdoor environments and detailed, beautiful indoors, highres textures, highpoly models ect.), combined it with an immersive and well-written storyline and
, licenced a quality physicssystem (Like Havok or Meqon) it would get REALLY interessting. The only thing that Doom3 lacked was a decent physicssystem, though it was not bad in comparison to other games. Even though Source some very advanced physics, I definently see more potential in the Doom3 engine, if used correctly.
That aside, I REALLY look foward to HL2, and although the engine won't be as revolutinary as it would have been a year ago, it was still produce fantastic graphic scenes, I'm sure