I suspect, if my own experience with friends is any indication, that acceptance of eReaders will be slow but steady among retirees who are technologically challenged. I have shown several pBook fans my eReader and they were amazed that you could read a book and actually choose a font size that you can see, and you don't need a bookmark!
Many pBooks, especially in paperback format, are small font sizes which are becoming a real issue with elderly people with failing eyesight. On a recent trip to my favorite used book store with an old friend, she passed over several books she said she wanted to read but couldn't because the type size was too small. And then there's the ability to vocalize the text which, although still mechanical and without proper inflection, nevertheless opens up new worlds for the visually challenged, if that's your only option.
As long as there are technological restrictions (surmountable but difficult for most) to sharing eBooks, pBooks will survive for reference, sharing and display.