As I said in the thread I started, when the HP audiobooks came out Apple made a Harry Potter special edition iPod. It is NOT a stretch to add Sony + JKR + HP eBooks (finally) + a new HP Sony reader. Sure it's wishful thinking, but it's really not a huge leap.
HP has a massive following of all ages and incomes. People collect all kinds of things. A Harry Potter themed reader would be a very big deal. Many Potter fans have read the series numerous times. The appeal of being able to carry all 7 books and to make notes and highlights of favorite passages or for discussion in one little device (compared to the size & weight of the entire series) is a huge, huge deal.
Quote from the JKR & Sony Pottermore press release:
"As the Pottermore Shop develops, it is intended that it should include further products designed specifically for Harry Potter fans, offering a potential outlet for Sony products and services related to Pottermore."