From an interview on MTV.com:
"In 2007, Lucas will begin work on a live-action "Star Wars" show set during the 18-year gap between Episodes III and IV. "We haven't started yet; I start that next year," the filmmaker said, adding that he's determined to write an entire first season before shooting begins on the show that will star "background" characters from that time period.
"None of the Skywalker story, none of that stuff is in there," he explained, shooting down any depiction of a young Han Solo acquiring the Millennium Falcon or running with Lando Calrissian. "It's completely different. The animated series has got all the characters in it. The one that comes after, the live-action one, is with people who were in 'Star Wars,' but they're not the main characters."
Lucas said the plot will be steered by characters such as Tie-Fighter or Rebel pilots, most only briefly glimpsed in the six "Star Wars" films."
Doesn't sound like a compelling way to bridge the gap of EPIII and EPIV... But maybe that's just me. I would prefer to have stories about the building of the Empire, start-up of the Rebellion, stories of young Luke and Leia, follow-up on Obi-Wan and Yoda. Maybe I should reserve judgement until we get more details of this, but right now, I'm pretty disappointed.