If Sony were to release a new reader they would be taking out the older model (505) and cutting down prices on the most recent (700).
What I feel is that they might take a totally different tack. A new kind of device.
Personally I think that with so much going on in technology, a one application device will have no place anymore. Smartphones are an excellent example.
Sony will still sell ebooks. What we'll read them on will be different.
Vaio is strong, Umpc is gone, reader is going away... some new powerful device encompassing all those is on the way. Some newer type of display with the best atributes of all of them? A new type of eink? Color?
This is an interesting wait.