Then there is Palpatine. Though I take it as read that Palpatine and Darth Sidious are one and same (and seem to recall canon support for this, beside fact that it just seems so totally obvious), I have also heard possibility voiced that they are different people. It doesn't seem at all likely to me, but maybe Lucas has some little strings he can pull to show up full picture, like some complex origami fold which requires one last simple tug to unfurl a vast tangle of deceptive brilliance. I'm not holding my breath.

Taking line of thought used for Mace Windu, as Padme is not mentioned in Trilogy, she either dies or goes into hiding and becomes totally unimportant to rest of series; latter seems highly unlikely. Padme's last major contribution to story is delivery of Luke and Leia into Galaxy, but once that bit of established "history" is out of way, anything could happen. Since Vader is unaware of locations or perhaps even existence of his children, Anakin probably won't know about birth or perhaps even conception. It is likely that Padme leaves him shortly thereafter, once he has revealed that his inner darkness isn't something she can help him defeat.

There are a few other bits which don't necessarily have to be addressed in this story. One is change from clone troopers to stormtroopers; since stormtroopers seem to be normal citizens of Empire, it shouldn't be same group of people. Somewhere along way Palpatine must make this change, probably as supply of clone troopers dwindle, but there is no reason Lucas would have to put it in Revenge of Sith. Also, of course, ships, vehicles, and armor shown in Attack of Clones are quite similar to those used by Empire in later years, Imperial designs evolved from those of Clone Wars. Since this would take some time to change, it will probably not be shown in Revenge.

To summarize: Anakin and Obi-Wan fight, and Anakin probably gets hurt; more Jedi die, possibly at hands of Anakin later in movie; Obi-Wan and Yoda survive and set up Luke and Leia for their roles in Trilogy; Palpatine may choose this time to reveal his inner darkness to Galaxy, now that it's too late for them to do anything about it; and Mace Windu and Padme probably die. Most likely Clone Wars are still raging, so we can count on them to infuse movie with action, and since Empire is on rise, we can assume that movie will have a darkening theme, though with light at end of distant tunnel in form of Skywalker twins. It'll be interesting to see how Lucas manages to pack all of this into one movie. But will movie satisfy gads of millions of fans? Only time, and power of Force, will tell.