For the 3rd edition, I used Eclipse for both development of the Java examples and to prepare the Latex manuscript (using the Eclipse Latex plugin TeXlipse).
I really prefer using IntelliJ for Java development and TeXShop (Mac OS X only) for editing Latex files so I just converted my writing setup.
I have a fairly good idea of what new topics I want to cover but I am still deciding what material from the 3rd edition I want to remove.
Since I released the 3rd edition over three years ago, I have averaged about 300 downloads of the free PDF version a day with a few sales of the print edition each month. I like making a free version available for people to read and generating traffic for my web site where I advertise my consulting services is great. Unfortunately, in the last couple of years when I see my book in search results it is very often on someone else's web site which violates the conditions of the Creative Commons non-commercial use license for the PDF version of my book.
My Latex setup supports output of PDF, HTML, and HTML with automatically generated embedded Google ads. I might change my mind, but I think that the free version of the 4th edition will be HTML pages on my web site, perhaps with a few Google ads, but probably not. I'll continue to sell print copies of my book on Lulu and also offer a PDF version for a few dollars.