Just popping in with random tidbits I've heard. Turns out 98PaceCar that they were actually looking at Charles Martinet (at least that was strongly hinted at in the Original Gamer Podcast #42) but he backed out because of "concerns of answering questions in SGC's atmosphere" or something to that effect. Whether or not that's true is another matter but it sounds like they tried. There's still a mystery guest remaining (may not necessarily be a voice actor), but whether or not it's someone big from the industry remains to be seen.
They've posted their floor plan for this year:
http://i.screwattack.com/content/ima...1274945756.jpg
It looks like the console gaming room may be a little smaller, which could be bad considering the arcades will now be sharing space there as well. But overall they have branched out a little bit, but if they run a good show this year then I can't imagine they'll hang around at the Westin DFW for too much longer as it can't possibly accommodate a significantly larger attendance that may come as a result of word of mouth/good reviews/etc.
There's also a mystery game planned for the Iron Man of Gaming 2010 that "nobody has played yet". Last time this happened was at the 2008 event where they had Guitar Hero: Aerosmith a few days before it came out. Hopefully it's a bit more than that, we'll see at the show.