Pablo Hidalgo answered a round of questions in the General Hyperspace Q&A Drop Box on December 5th. Here are a few of the questions he answered:

When can we expect the next Episode III trailer?
Probably around March, about the time of the release poster.

About the recent site databank updates - is the photo of General Grievous a completed shot from the film, or just done for that purpose? Has the look and voice finally been decided on?
Yes, it's one of several final shots -- although appearing at web resolution hardly does it justice. His look has been locked down for a while, though his voice has yet to be determined.

I love Anakin's evil sith eyes in the teaser trailer - could you confirm if that is in the film - that is, that he has those eyes at some point, or is it just a special shot for the trailer?
It's from the film; it's not a shot specifically created for the trailer. No shots were created just for the trailer -- however, some shots were completed to a certain degree just for the trailer. That is, expect several shots to look different in their final film incarnation.

How many teaser poster concepts were there? How did that one get chosen...?
I saw at least two dozen, and there were many more than that. A number of factors resulted in the final choice, including the input of a focus group that indicated that the final had the broadest appeal.

You can read more of the question he answered at the link above.