I agree with most of your estimates. The only one with which I disagree is the 2, I would put it near the level of the 1, maybe at 90%, but doesn't matter much. You're reasoning on 5 years, which is a relatively short time frame, but that's not the main problem either.

There are two problems which are not really accounted in your estimates, IMHO :

1. Black Swans : the probability is very low, but we can't rule out some catastrophic outcome, like fanatics (from Tea Party or whatever) seizing power and wanting to ban evolution-related books. The odds are very low, but who would have predicted Stalin, Pol Pot, Hitler or the Rwanda genocide ? I just don't want anyone to hold the power to massively terminate copies of books easily, even if I'm pretty sure they won't use that power. Because I'm just "pretty sure" of it. So I want to steer the future in a direction in which they just can't hold the power. A dystopia like The Right to Read is not impossible either. And yes I know about the fallacy of using fictional evidence, but let me use it as a lossy compression to convey a concept in a few words.

2. The actual consequences of DRM, even without any intent to abuse from them : you can't (easily) lend or give the ebooks for example. And what about the future ? When your Kindle dies in 10 years, what's the chance that you can't transfer the ebooks on the new device you bought ? Those problems are real and serious too.