Amazon is not a device company, has never been a device company, and has no intention of becoming a device company. It would only acquire a boat anchor like webOS if it had no reasonable alternative (and even then I doubt it). It has plenty of alternatives.
Kindle as a device is simply a near term means to an end: To ensure that there are phenomenal ways for consumers to access the Amazon cloud services.
Amazon has no desire to make $ directly off of devices. It has been happy to sell them at a loss, and will continue to be happy to (to a point). They will also continue to be happy to invest in great experiences that run on other devices (Kindle software for iPhone/iPad/Android/WP7/PC/web as well as the Amazon.com store).
Repeat after me: Stop focusing on the device. Device centric computing is done.
Cloud+Devices+People is the future. Amazon knows this as well as anyone and is in a great position to capitalize on it.