As bad as the whole "Leia is Luke's sister" retcon is, I feel that re-retconning (Or should that be de-retconning?) her back into a character who isn't related to Luke would be worse. Besides, what would be the point? To reignite the Luke/Leia/Han love triangle? Han won Leia at the end of ROTJ -- why upset that relationship, especially at the ages they are at now?
The damage has been done; just let the wound heal and move on.