I love my ereader and I love ebooks.
I know many people who prefer paper and many who are ambivalent and some who actually prefer ebooks. Age does not seem to matter. My mother who is 87 loves her ereader, but has no problem with paper either. I know children under 10 who read both. These I would class as ambivalent. Not undecided, just are happy with either.
Myself, I would be devasted to have to go back to paper for fiction. I still am fine with newspapers and magazines in print. I've never been fond of hard covers, as I find them cumbersome, but technical books and non fiction are okay either way. So I am some sort of weird hybrid reader I guess.
I would think that a reputable responsible polling company/person would disqualify those who didn't read at all, or didn't read anything but the TV Guide, but who knows. I would disqualify all who had never tried an ereader
Ultimately it is the children of today who will decide. When someone markets a GI Joe or My Little Pony ereader successfully we will know the time has come.
Helen