Here's an article posted over at CNBC which states that Sony will be announcing two new readers AND discontinuing the 505.
http://www.cnbc.com/id/32289759/for/cnbc/
They're also reducing the price of books in their bookstore to be in line with Amazon's 9.99 pricing.
I just skimmed the article, but didn't see any mention of a date the new models will be available.
dordale