Topic vesus content.
Your topic is what's next but in your post you want to convert what you have. So let's cover both.
1. What's next is the same story we saw in the land of MP3. I expect ebooks to decimate the printed book business now that ereader hardware has matured.
2. Given newer readers handle unprotected PDFs with some ease that's what is next for those that don't want to be locked down. But the publishers and authors know this is a sure way to never see a dime for their works.
3. http://news.cnet.com/8301-13579_3-20006383-37.html in short iPad. Let me add that my kindle books showed up without a fuss and no need for conversion.
4. In conclusion, you appear to want PDFs.