TheForce.net have been scooped by one of their readers with a description of the next trailer for Star Wars: Episode III - Revenge of the Sith, which has been speculated to be released within the next month.
(PLEASE NOTE: If you're avoiding spoilers, we advise you NOT to read on)
The trailer begins with the following exchange:
Palpatine: "The Dark Side of the Force is the pathway to many abilities some consider to be unnatural."
Anakin: "Is it possible to learn this power?"
Palpatine: "Not from a Jedi."
We are then introduced to the political maneuvering of Palpatine, Obi-Wan and Mace Windu. All of them actually want to use Anakin as a pawn in their game (Palpatine makes Anakin his "personal representative on the Jedi Council" while Obi-Wan wants him to "report on all the Chancellor's dealings"). The first minute or so is surprisingly heavy on dialogue and consists mostly of shots of various characters speaking to each other (intercut with short glimpses of evil droids, space battles etc.). We even see how Mace Windu and three other Jedi attempt to arrest Palpatine (he grabs the lightsaber and confronts them). When Mace Windu tells Anakin "You are on this council but we do not grant you the rank of Master", Anakin loses it and joins the Dark Side (Sidious: "Every single Jedi is now an enemy of the Republic"). At least that's how the trailer makes it look.
Then the more "visual" half starts with some very neat scenes like a low angle shot of Anakin marching in front of a Clone trooper army. We see Wookiees on some kind of war machine, the duel in the volcano field, gigantic 10-wheel military transports and actual destruction of the Senate chamber. Everything is very dramatic, several deaths are implied, Padme is seen crying loudly and music from the Emperor duel (ROTJ) is heard.
Overall, the first half of the trailer is surprisingly specific, making no sense whatsoever to people who don't know Star Wars well. The second half is very dark and dramatic, but with lots of action. Bad guys (apart from Sidious) only appear for a fraction of a second and have no lines. The final seconds consist of Obi-Wan shouting "You were the chosen one!", fighting Anakin while both dangle from some ropes/wires. After the closing titles, there is a bonus shot of Vader and Sidious standing side by side, accompanied by Vader's breathing.
This is a preliminary version with effects and sound not quite finalized. One part of the trailer is actually without music (either for dramatic effect or John Williams' new score will be inserted here?). The length is little under 2:30.
When further questioned about the "evil droid", our source confirmed that there wasn't a clear shot of General Grievous but there was one of the bodyguards:
There is some evil-looking humanoid droid with a cape around his head and torso, flanked by two classic battledroids (from Episode I). He seems to hold a lance in his hand. Later, Obi-Wan is seen swordfighting with a humanoid droid but he's only seen from back and moving quickly. (I'm 90% certain it IS Grievous, but it's extremely short and quick shot.) Anyway, both of these shots are VERY brief (about half second).
One of the shots depicts Obi-Wan being surrounded by dozens of droids. Some of them look different and wear capes, maybe one of them is Grievous. But it's very wide shot, the characters are small.