Quoted from CraigC:
So you want to see a fat old Carrie Fisher running around still trying to be relevant to the rebellion?
Yeah it's 20+ years too late to have the original cast star in these movies. The cameo approach is OK, though it has to be handled delicately or it will just be lame and distracting. The new movies have to stand on their own, and I hope they just take advantage of the Star Wars universe as a great setting rather than trying to mooch off the legacy of the original series.
At least there's the positive development that Disney rejected George Lucas' ideas for the new film. He's been creatively tapped out for 30 years.