Bottom line, I doubt very much that we will be using ePub/mobi 20 years from now.
In its current form, I have and enjoy a smartphone, ereader, iPad, and a laptop. I hope that within twenty years we can cut back to one or two devices. This will also likely lead to software changes.
I don't care if you use Sony, Apple, Amazon, or Barnes and Noble; the odds are that some (most? all?)of us will wake up one day to discover we own a bunch of books in an obsolete format.
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