It has been announced that the new Star Wars movie will be filmed in Britain at Leavesden Studios. Although building work at the studio isn't finished, the owners are confident that it will be ready before the principal shooting starts in Autumn 1997.
There is so much information/misinformation about this film that anything we say is merely conjecture. So here goes:
The film is set during the clone wars, around 30 years before the original Star Wars movie. It does feature Obi Wan Kenobi, Anakin Skywalker and Yoda, Carrie Fisher is said to have a cameo role, and is also reported to be one of the many people lending a hand to the script. Shawshank Redemption writer Frank Darabont has said he was approached to help out with one of the chapters in the trilogy, although Lucas has not officially announced the names of anyone else involved with writing the project.
Lucas has said, though, that he wants this trilogy to have a darker theme encompassing friendship and betrayal as the old Republic is destroyed by the Emperor's forces. It's believed that Industrial Light and Magic has been working on new effects techniques (some of which will be seen in the re-released first trilogy) for the last few years. Also Fox has converted a large lump of land in Australia into a studio complex for work on a 'major new project.' Make of that what you will.
Oh, and the rumour about Kenneth Branagh starring as the younger Obi Wan seems to be false. Both he and Lucas claim the first they knew about it was reading the press reports.