From what we've see over the months, lying and obscuring the truth seems to be a way of life for all members of the Anthony family. I have no doubt that this has been a method of coping with issues within the family for many many years.
Casey didn't just become a lying, manipulative, murderous, sociopath in the last year. I'm sure there's been many behavioral problems with Casey from a very early age. The immediate family, with Cindy leading the way, has sought to put on a public front of a happy, normal family. But in private, within the family, they were dealing with many serious issues.
If the video-taped jailhouse visits are any indication of how George and Cindy dealt with Casey over the years, it's clear that they allowed Casey to be in charge and manipulate them. It's doubtful that they ever disciplined Casey, making her take responsibility for her actions and suffering the consequences.
The only indication we have that Cindy ever took any decisive steps to doing something constructive, is the report that she was seeing a counselor who had recommended kicking Casey out of the house and Cindy seeking custody of Caylee. But this was in the months leading up to Caylee's disappearance and death, and was far too late.
So, I can't see George and Cindy doing a complete turnabout and now telling the truth. They need a professional counselor to deal with all the issues they've swept under the carpet for more than 20 years.