Swift 2 was a big update and required more changes in Functional Programming in Swift than we originally thought. We've finished the bulk of the work though and a beta version of this update is already available to all eBook customers who bought the book through our website. Just use the download link in the original receipt (from Gumroad) to download the beta PDF.
We still have to do another round of edits, and the changes need to go through copy-editing before we're ready to make the new version available as paperback, Kindle, etc.
Meanwhile, our new books Advanced Swift and Core Data are on the finishing straights as well. We plan to be done content-wise by the end of the month. Then we'll need a bit more time to finish up copy-editing and some design work, before the final eBooks and the paperback version will be available -- we're still aiming for November, fingers crossed!
Last but not least, we want to send a huge thank you to all the people who have already bought the early access versions of Advanced Swift and Core Data. Your support makes these projects possible!
Best from Berlin,
Chris, Florian, and Daniel