If Kindle had, instead, become obsolete that day, and was no longer supported, the Kindle users would have been just as out of luck as they are under the deletion, because there is no obligation for them to keep supporting old tech.
Otherwise, we'd have had successful consumer lawsuits over continued support of 8-tracks, reel-to-reel, Beta and other now-defunct media tech.
And I'd have been able to sue Microsoft when they stopped supporting a particular spreadsheet/WP program in favor of what is now known as Office...and didn't provide any way to convert the data into the new format. I lost years of personally generated data and my Father had to spend thousands in order to convert files for his business.
But no such victories exist.
While the impetus is different, the outcome is likely to be the same.
Amazon remotely deleted Kindle files of books they shouldn't have in the first place, and in at least most cases, refunded the money.
Look at it this way- if you bought a book that turned out to be stolen from a bookstore, that could be confiscated without recompense. Your only viable lawsuit would be against the thief. If you won, you'd get your money back...and nothing else.
Here, the Kindle users got their money back in exchange for their deleted files...the identical legal position to the person who successfully sued the thief over the confiscated stolen property they purchased from him.
My guess is that the lawsuits will go nowhere. They have no more recourse than I would if the Mods here deleted all the threads I've subscribed to...some of which contain my original creative work that I have never published anywhere else, nor copied onto my own hard drive via Word or a similar program.
The public relations nightmare, OTOH, may have longer legs.
IMHO, Amazon erred by doing what they did the way they did. They should have notified potentially affected customers ahead of time- ideally at least a month in advance- in order to let them make whatever adjustments they needed to before the deletion. Adjustments like transferring one's cribnotes to a physical copy, for instance.