Note that Sony have nearly ceased in their making available new ebook titles at their store in the past month:
https://www.mobileread.com/forums/showthread.php?t=16810
One possibility is that they are waiting for the existing devices to all be sold and then they might announce that they are exiting the business. Another possibility is that these are separate issues which have their own explanations - like a new device model about to be released and a new method of delivering ebook titles to customers.