The PRS-505 supports ePub. Can't remember if that was after a firmware update or from the factory though. And even after the Sony ebook store closed down they let you transfer everything to Kobo. And you can still sideload ePubs on with Adobe Digital Editions.
Early Kindles are going to lose a lot of functionality soon as 3G networks get shut down and they have no WiFi to fall back on.
Early Kindles are going to lose a lot of functionality soon as 3G networks get shut down and they have no WiFi to fall back on.