My Dad, in his late 80s, is redoing the Watson family video. About 1 hour of media. Dad (still a member of the US National Academy of Science) has a quirky sense of humor: he likes to mix in Poser 3D animations with his videos so his favorite virtual character, 'Hank' an acerbic gorilla, keeps chiming in to my family history. Fortunately, Roger Ebert will never see this :-)
I'm still too busy being wow'd by the implications of color video and widespread photography. Of my grandparents, I have a few black-and-white's from their late 20's. Of my parents, a couple off-color's from their early 20's.
My decedents (if I have any) will have full, accurate color video and photo from a ton of points in my life.
Forget recording who I was and what I did- it still blows my mind to imagine 'knowing' your parents as they were when they were young. Images are the first step to this; they make the past real.
images are a big piece, but what i'm suggesting is that it will get to a point where you can actually interact with your dead grandparents. think about predictive AI on these data sets... it's going to be way more rich than images alone...